## Definition of INTERIOR ANGLE

Recent Web-based illustrations Both constructions are three-dimensional, yet their geometries are vastly different: Their floor plans are distinct, the curvature of their exteriors is different, and the angles of their interiors are varied as well. —Quanta Magazine, published on April 9, 2018 Both constructions are three-dimensional, yet their geometries are vastly different: Their floor plans are distinct, the curvature of their exteriors is different, and the angles of their interiors are varied as well.

—Quanta Magazine, published on the 31st of October, 2019.

—Quanta Magazine, published on April 9, 2018 Both constructions are three-dimensional, yet their geometries are vastly different: Their floor plans are distinct, the curvature of their exteriors is different, and the angles of their interiors are varied as well.

—Quanta Magazine, April 9, 2018Both constructions are three-dimensional, however their geometry is vastly different from one another: Their floor plans are distinct, the curvature of their exteriors is different, and the angles of their interiors are varied as well.

—Quanta Magazine, published on January 6, 2015 Following are some sample sentences that were automatically generated from various internet news sources to reflect current use of the word ‘interior angle.’ It is not the opinion of Merriam-Webster or its editors that the viewpoints stated in the examples are correct.

## Interior Angles – Definition, Meaning, Theorem, Examples

Intersections of two parallel lines intersected by a transversal are also referred to as interior angles. Similarly, the angles that exist in the region bordered by two parallel lines that are intersected by a transversal are also referred to as interior angles.

1. | What are Interior Angles? |

2. | Types of Interior Angles |

3. | Interior Angles of a Triangle |

4. | Sum of Interior Angles Formula |

5. | Finding an Unknown Interior Angle |

6. | Interior Angles of Polygons |

7. | FAQs on Interior Angles |

## What are Interior Angles?

Interior angles can be generated in two different methods in geometry. One occurs when parallel lines are cut by a transversal, whereas the other occurs when parallel lines are not cut by a transversal. Angles are classified into distinct categories based on the measures that they possess.

There are additional sorts of angles that are referred to as pair angles since they must exist in pairs in order to display a specific attribute. Pair angles are defined as One type of angle is the interior angle. Interiorangles can be defined in two different ways:

- Angles within a Polygon:Interior angles are those angles that are contained within a form, which is often an apolygon shape. Figure (a) below shows that the internal angles (a, b, and c) are all the same size. Interior Angles of Parallel Lines (also known as internal angles of parallel lines): Intersections of two parallel lines by a transversal are also known as interior angles, and the angles that fall within the region contained by two parallel lines are also known as interior angles. (b) In the image below, the letters (L 1) and (L 2) are parallel, and the letter L is the transversal. The angles 1, 2, 3, and 4 are all internal angles
- The angles 1, 2, 3, and 4 are all exterior angles.

## Types of Interior Angles

There are two sorts of interior angles that are generated when two straight lines are sliced by a transversal, and they are alternate interior angles and co-interior angles. Alternate interior angles are the most common type of interior angle.

- Intersection of Two Parallel Lines by a Transversal: When two parallel lines are crossed by a transversal, alternate interior angles are generated. This non-adjacent pair of angles is produced on the transversal’s opposing sides, and they are not next to one another. The pairs of alternate interior angles shown in the preceding image (b) are 1 and 3, 2 and 4, and 3 and 5. If two parallel lines are intersected by a transversal, the lengths of the lines are equal. Co-InteriorAngles: These angles are a pair of non-adjacent internal angles on the same side of the transversal that are not contiguous to one another. The pairs of co-interior angles shown in the preceding image (b) are numbered 1 and 4, 2 and 3, and 3 and 4. They are also known as same-side internal angles or consecutive interior angles, depending on how they are formed. Due to the fact that the total of two co-interior angles equals 180o, they also form a pair of supplementary angles.

## Interior Angles of a Triangle

At each vertex of a triangle, there are three internal angles to be considered. The total of all of these internal angles is always 180° in each case. The intersection of the bisectors of these angles is known as the incenter. In a triangle, because the total of its internal angles equals 180°, there is only one possibleright angleorrobtuse angle that can be formed in each triangle. A triangle with all three acute interior angles is known as an acute triangle, a triangle with one obtuse interior angle is known as an obtuse triangle, and a triangle with one right angled interior angle is known as aright angled triangle.

## Sum of Interior Angles Formula

For example, from the smallest polygon, such as a triangle, to an endlessly complicated polygon with n sides, such as an octagon, all of the sides of the polygon combine to form a vertices, and each vertices has an interior and exterior angle. According to the angle sum theorem, the sum of all three internal angles of a triangle equals 180° when all three angles are equal. The total of the internal angles of every polygon may be calculated by multiplying the number of sides by two less than the number of sides times 180°.

A polygon is defined as follows: S = sum of internal angles n = total number of sides of the polygon When we apply this formula to a triangle, we obtain the following result: S = (n 2) x 180°S = (3 x 2) x 180°S = (1 x 180°S = 180°S = 1 x 180°S = 180° The sum of the internal angles of polygons is determined using the same method as the sum of their exterior angles:

Polygon | Number of sides, n | Sum of Interior Angles, S |
---|---|---|

Triangle | 3 | 180(3-2) = 180° |

Quadrilateral | 4 | 180(4-2) = 360° |

Pentagon | 5 | 180(5-2) = 540° |

Hexagon | 6 | 180(6-2) = 720° |

Heptagon | 7 | 180(7-2) = 900° |

Octagon | 8 | 180(8-2) = 1080° |

Nonagon | 9 | 180(9-2) = 1260° |

Decagon | 10 | 180(10-2) = 1440° |

## Finding an Unknown Interior Angle

Using the “Sum of Interior Angles Formula,” we may get the interior angle of a polygon that is unknown. Consider the following example in order to determine the angle x that is missing from the following hexagon. The total of the internal angles of a hexagon is 720° when the interior angles of a polygon table are given in the preceding paragraph. Two of the hexagon’s internal angles are right angles, as seen in the diagram above. As a result, we have the following equation: 90° plus 90° plus 140° plus 150° plus 130° plus x Equals 720° Let’s see if we can figure out what x is by solving this.

## Interior Angles of Polygons

When all of a polygon’s sides and angles are congruent, the polygon is said to be an irregular polygon. Some instances of regular polygons are shown below. For a polygon with ‘n’ sides, we already know that the total of the interior angles of a polygon is given by the formula 180(n-2)°. In a regular polygon with ‘n’ sides/vertices, there are ‘n’ angles to be found. In a regular polygon, because all of the interior angles are equal, each interior angle may be calculated by dividing the total of the angles by the number of sides of that polygon.

Let us try to use this formula to get the internal angle of a regular pentagon and see how it turns out.

In a regular pentagon, the interior angles may be calculated by dividing by n and using the following formula: ((180(n-2))/n° = ((180(5-2))/5)°= (180 (3)/5 = 540/5= 108° As a result, the internal angle of a regular pentagon is equal to 108°.

The inner angles of polygons are determined using the same formula as the outside angles, as follows:

Regular Polygon | Sum of Interior Angles, S | Measurement of each interior angle((180(n-2))/n)° |
---|---|---|

Triangle | 180(3-2) = 180° | 180/3 = 60°, Here n = 3 |

Square | 180(4-2) = 360° | 360/4 = 90°, Here n = 4 |

Pentagon | 180(5-2) = 540° | 540/5 = 108°, Here n = 5 |

Hexagon | 180(6-2) = 720° | 720/6 = 120°, Here n = 6 |

Heptagon | 180(7-2) = 900° | 900/7 = 128.57°, Here n = 7 |

Octagon | 180(8-2) = 1080° | 1080/8 = 135°, Here n = 8 |

Nonagon | 180(9-2) = 1260° | 1260/9 = 140°, Here n = 9 |

Decagon | 180(10-2) = 1440° | 1440/10 = 144°, Here n = 10 |

### Related Articles on Interior Angles

See the pages that follow for further information on interior angles.

- Vertical Angles
- Alternate Angles
- Alternate Exterior Angles
- Same Side Interior Angles
- Interior Angles of Polygon Calculator
- Vertical Angles
- Vertical Angle

Important Points to Keep in Mind When analyzing interior angles, the following are some important aspects to keep in mind:

- A polygon with n sides can have its inner angles added together using the formula 180(n-2)°
- This can be done using the following formula: For any interior angle of a regular polygon with a certain number of sides, the formula ((180(n-2))° may be used to compute it. A transversal intersecting two parallel lines, according to the alternative interior angles theorem, produces alternate interior angles that are identical for each pair of adjacent alternate interior angles. If, on the other hand, a transversal intersects two lines in such a way that a pair of internal angles is equal, the two lines are said to be parallel. If a transversal intersects two parallel lines, the co-interior angles theorem states that each pair of co-interior angles is supplementary (their total is 180°) and that each pair of co-interior angles is supplementary. When a transversal intersects two lines in a such that a pair of co-interior angles are supplementary, the lines are said to be parallel.

## Interior Angles Examples

- Example 1: In the accompanying diagram, get the internal angle at vertex B by using the formula. Solution: Because the number of sides of the given polygon is n = 6, it is classified as a hexagonal polygon (Hexagon has 6 sides). This polygon has 720° as its sum of internal angles since its n-2)o.= 180(6-2)= 180(4-2)o. = 180(6-2)= 180 4 = 720° Knowing that the total of all the internal angles in this polygon equals 720°, we may proceed to the next step. In the following polygon, the total of all the angles is as follows:A + B + C + D + E + F= (x – 60) + (x – 20) + 110 + 120 + 130 + (x – 40)= 3x+ 240 Now, we’ll put this total equal to 720 and work out what the value of x is. 3x+ 240 = 7203x = 480x = 480/3 = 160 3x+ 240 = 7203x = 480 Let’s try to locate B now. In this case, B = (x – 20)° = (160 – 20)° = 140°. The internal angle at vertex B is thus b=140°
- Example 2: In the accompanying picture, MN || OP and ON || PQ are represented by the letters MN and ON respectively. If MNO=55°, then determine the value of OPQ. Solution: We will make the lines in the given figure longer by extending them. MN || OP is a transversal in this case, and ON is also a transversal. As a result, the angles 55° and x° are co-interior angles, and as such, they are supplementary (by co-interior angle theorem). as an example:55 degrees plus x degrees equals 180 degreesx degrees equals 180 degrees less 55 degrees equals 125 degrees ON || PQ and OP are both transversals once more. As a result, x° and OPQ are equivalent angles, and as a result, they are equal. For example, OPQ = x=125°, which results in OPQ=125°.

Continue to the next slide proceed to the next slide Simple graphics might help you break through difficult topics. Math will no longer be a difficult topic for you, especially if you visualize the concepts and grasp them as a result. Schedule a No-Obligation Trial Class.

## FAQs on Interior Angles

Interior angles are those that are found within the boundaries of a polygon. The internal angles of a triangle, for example, are three. Interior angles may also be defined as “angles confined in the interior area of two parallel lines when they are crossed by a transversal,” which is another way of saying it.

### How to Find the Sum of Interior Angles?

It is possible to calculate the sum of interior angles in a polygon using the formula 180(n-2)°, where n is the number of sides in a polygon. When calculating the sum of interior angles of a quadrilateral, we may substitute n with 4 in the formula to get the result. We will have 180(4-2)°= 360° as a result.

### What is the Sum of the Interior Angles of a Heptagon?

A heptagon is a polygon that has seven sides and seven angles on each side. 900° is equivalent to 180(7-2)° because the total of all the internal angles of a heptagon equals 180(7-2)°. This results in a heptagon’s internal angles adding up to an impressive 900 degrees.

### What is the Sum of the Measures of the Interior Angles of a 27-Gon?

It is 180(27-2)° when the total of the measurements of the inner angles of a 27-gon is calculated. It is equivalent to 180 x 25, which is 4500° in radians.

### How to Solve Same Side Interior Angles?

When two parallel lines are cut by a transversal, the interior angles on the same side of the lines are additional. This implies that their total is 180 degrees. As a result, in order to solve such angles, we will make use of this characteristic and determine the missing value.

### What is the Sum of the Interior Angles of a Polygon?

By using the formula 180(n-2)°, it is possible to find out how many internal angles there are in a polygon with n sides. It aids in the calculation of the entire sum of all the angles of a polygon, regardless of whether it is a regular polygon or an irregular polygon. We can also check the angle sum property with the help of this formula as well. When you add up all of the interior angles of a triangle, you get 180o, when you add up the internal angles of a quadrilateral, and so on.

### What is the Sum of the Interior Angles of a Triangle?

To compute the sum of the interior angles of a triangle, we will use the sum of internal angles formula S = 180(n-2)°, where n is the number of sides of a polygon and S is the sum of inner angles formula. Because the triangle has three sides, the number n equals three. As a result, 180(n-2)° = 180(3-2)° = 180° is the sum. As a result, the total of the internal angles of a triangle is equal to 180 degrees.

### What is the Sum of Interior Angles of a Hexagon?

To find the sum of the interior angles of a hexagon, we’ll use the sum of internal angles formula S = 180(n-2)°, where n is the number of sides in a polygon and is the number of sides in a hexagon.

Because the hexagon has six sides, the number n equals six. As a result, the total is 180(n-2)° = 180(6-2)° = 180 4 = 720° (180(n-2)°). As a result, the total of the inner angles of a hexagon equals 720 degrees.

### How Many Interior Angles Does an Octagon Have?

An octagon has eight sides and consequently, it has eight internal angles. In an octagon, the total of the eight inside angles is 1080 degrees.

### What is the Sum of all Interior Angles of a Pentagon?

To find the sum of the interior angles of a pentagon, we’ll use the sum of internal angles formula S = 180(n-2)°, where n is the number of sides in a polygon and is the number of sides in a pentagon. The number n is 5 in this case since the pentagon has 5 sides. As a result, 180(n-2)° = 180(5-2)° = 180 3 = 540° is obtained. As a result, the total of the inner angles of a pentagon is equal to 540 degrees.

## Interior Angles of Polygons

Here’s another illustration:

## Triangles

The sum of the interior angles of a triangle equals 180°. Let’s try a triangle for a change: 180° is equal to 90° plus 60° plus 30°. It is effective in this triangle. Tilt a line by 10 degrees now: 180° is equal to 80° plus 70° plus 30°. It is still operational! One angle increased by 10°, while the other decreased by 10°.

## Quadrilaterals (Squares, etc)

(A quadrilateral is a shape with four straight sides.) Let’s attempt a square this time: 360° is equal to 90° plus 90° plus 90° plus 90°. The sum of a square is 360 degrees. Tilt a line by 10 degrees now: 80° plus 100° plus 90° plus 90° equals 360°. It still adds up to a whole 360 degrees. Quadrilaterals have interior angles that sum up to 360 degrees.

### Because there are 2 triangles in a square.

The internal angles of a triangle sum up to 180°. and the interior angles of a square add up to 360°. because a square may be formed by joining two triangles together!

## Pentagon

Because a pentagon has five sides and can be constructed from three triangles, the internal angles of a pentagon sum up to three 180° angles, or 540°. If the pentagon is regular (all angles are the same), then each angle is equal to 540°/ 5 = 108° (Example: verify that each triangle here adds up to 180°, and check that the pentagon’s inner angles sum up to 540°). All of the inside angles of a Pentagon come together to equal 540°.

## The General Rule

If we add a side (a triangle to a quadrilateral, a quadrilateral to a pentagon, and so on), we increase the total by another 180 degrees: As a result, the general rule is as follows: The sum of interior angles equals (n2) 180 degrees. For each angle (of a Regular Polygon), the formula is: (n 2/180 °/n Perhaps the following illustration will be of assistance:

### Example: What about a Regular Decagon (10 sides)?

In the sum of interior angles, (n 2) 180 degrees equals (102) 180 degrees equals 8 180 degrees equals 1440 degrees. And for a Regular Decagon, the following is true: Each inner angle is equal to 1440/10 =144°. Please keep in mind that inside angles are frequently referred to as “Internal Angles.”

## What Are Interior Angles? – Definition & Examples

Whenever Tashmina was a small girl, she dreamed of growing up and decorating the interiors of people’s houses. She enjoyed rearranging the furniture in her room, including the bed, the dresser, the bookcases, and her stuffed animals. When she was older, she pursued a career in interior design by enrolling in courses. When Tom was younger, he wished to contribute to the preservation of national parks, lakes, and rivers. When he grew up, he began working for the United States Department of the Interior (DOI).

- Interior?
- Consider the implications of this.
- The Department of the Interior is in charge of the parks that are located within the county.
- Angles and forms have an inner and an outside, just as your house has an inside and an outside (interior and exterior).
- An internal angle can be found in any shape or design when two lines come together.

The internal angles of a rectangle are equal to the number of corners it possesses. Because a hexagon has six corners, it has six interior angles, and each angle has one internal angle. Because a hexagon has six interior angles, it has six interior angles.

## Definition of interior angle

This indicates the grade level of the word based on its difficulty. This indicates the grade level of the word based on its difficulty. nounGeometry. an angle produced between two parallel lines by the intersection of a third line with the first two an angle created by two neighboring sides of a polygon within the polygon EVALUATE YOUR KNOWLEDGE OF AFFECT AND EFFECT VERSUS AFFECT! In effect, this exam will determine whether or not you possess the necessary abilities to distinguish between the terms “affect” and “effect.” Despite the wet weather, I was in high spirits on the day of my graduation celebrations.

## Origin ofinterior angle

The first written document dates back to 1750–60.

## Words nearbyinterior angle

Interim denture, Interim Standard Atmosphere, interinsurance, interionic, interior, interior angle, interior decoration, interior decorator, interior design, interior designer, interior drainageDictionary.com provides a comprehensive list of terms and definitions for interim denture, Interim Standard Atmosphere, interinsurance, interionic, interior, interior angle, interior decoration, interior decorator, interior design, interior designer, and interior drainage.

Unabridged Random House, Inc.

## How to useinterior anglein a sentence

- In each of the families, there is a parameter that can be adjusted in an unlimited number of ways to make some interior angles smaller and others proportionally bigger while still keeping the ability to tile space. The gunman appears to have fired the shot through the glass, according to the internal footage. One of its most senior officers is currently serving as Baghad’s minister of the interior. I was asked to do this Hemingway part with the white stubble by Brazakka, my boat’s skipper, and he specifically requested the hero viewpoint.

- As more than 300 police motorbikes from dozens of jurisdictions drove by Justin, he peered through the gloomy inner window. In recent weeks, Isaacs has returned from the New Mexico desert, where he was filming interior sequences for a new television mini-series called Dig. The interior of the omnibuses was ornamented with a life-size replica of Mrs. Charmington herself
- Every room had some sort of water feature, whether it was a small fountain in the center or four smaller ones arranged in a circle around the space. The remaining work is accomplished by removing two higher and four lower teeth and replacing them with fake ones at the proper angle. I don’t know much about the interior design of Kullak’s conservatory because I only attended his own classes
- Yet, Intense contrast between the wide street and the contained stuffiness of the gloomy and crammed interior.

## British Dictionary definitions forinterior angle

Any of the four angles formed by a transversal that reside inside the region between two crossed lines is referred to as an angle of a polygon enclosed between two adjacent sides. Complete Unabridged Digital Edition of the Collins English Dictionary, published in 2012. William Collins Sons Co. Ltd. was established in 1979 and 1986. In 1998, HarperCollinsPublishers published the following books: 2000, 2003, 2005, 2006, 2007, 2009, and 2012.

## Scientific definitions forinterior angle

When two straight lines are crossed by a third straight line, any of the four angles created inside these two straight lines can be used. An angle produced by two adjacent sides of a polygon that is contained inside the polygon is called a right angle. Examine the outside aspect. The American Heritage® Science Dictionary is a resource for those interested in science. The year 2011 is the year of the copyright. Houghton Mifflin Harcourt Publishing Company is the publisher of this book. All intellectual property rights are retained.

## Internal and external angles – Wikipedia

The term “interior angle” links to this page. See Transversal line for interior angles that are on the same side of the transversal as the transversal line. Angles both internally and outside In geometry, anangleof apolygonis created by two sides of a polygon that have the same terminus as one another. This angle is referred to as aninteriorangle(orinternal angle) for a simple(non-self-intersecting) polygon, regardless of whether it is convex or non-convex. If a point inside the angle is located within the interior of the polygon, the angle is referred to as aninteriorangle(orinternal angle).

The term “convex polygon” refers to a polygon whose internal angles are all fewer than 180 degrees (radians).

The opposite of this is anexteriorangle(also known as anexternal angleorturning angle), which is generated by one side of a basic polygon and a line drawn from the opposite side.: pp. 261-264

## Properties

- A vertex’s internal angle and its external angle add up to 180 degrees
- The total of the internal and external angles of a vertex is radians (180°). For a basic polygon with only one side, the total of all of its internal angles is (n –2) radians or 180(n –2) degrees, where n is the number of sides. Mathematical induction may be used to verify the following formula: Begin with a triangle, for which the angle total is 180°, and then replace one side with two sides that are joined at another vertex, and so on. The sum of the external angles of any simple convex or non-convex polygon, if only one of the two external angles is assumed at each vertex, is 2 radians (360°)
- If only one of the two external angles is assumed at each vertex, the sum of the external angles of any simple convex or non-convex polygon is 2 radians (360°)
- A vertex’s exterior angle is unaffected by which side is extended first: the two exterior angles that may be created at a vertices by extending alternately one side and the other are vertical angles, and hence have the same measure.

## Extension to crossed polygons

By employing the notion of directed angles, it is possible to apply the inner angle concept to cross-sectioned polygons such as star polygons in a consistent manner. A closed polygon with a total of n vertices and a strictly positive integerk is the number of total (360°) revolutions one would make by walking around the perimeter of the polygon, in degrees, is given by 180(n –2 k)°, where n is the number of vertices and k is the number of strictly positive integers that one would make by walking around the perimeter.

When walking around the perimeter of an ordinary convex polygon (or a concave polygon), for example, k= 1, because the exterior angle sum is 360°, and traveling around the perimeter requires just one complete rotation.

## References

- A generic formula for the interior angles of a triangle
- A formula for the interior angle sum of polygons In this Java exercise, the interior angle sum formula for simple closed polygons is extended to include crossing (complex) polygons, and the result is displayed interactively.

## Triangle interior angles definition – Math Open Reference

The angles on the inside of the triangle are referred to as the internal angles. Consider the following: To reshape the triangle, drag the orange dots on each of the three vertices (A, B, and C). It is important to note that the internal angles always sum up to 180°. All of the inner angles of a triangle add up to a total of 180°. This means that only one of the angles can be 90 degrees or more. Because one angle in a right triangle is always 90 degrees, the other two angles in a right triangle must always sum up to 90 degrees.

For information on the characteristics of the interior angles of a polygon with any number of sides, see interior angles of a polygon with any number of sides.

## Properties

- It is always possible to add up the inner angles of a triangle to 180°
- Because the internal angles always sum up to 180°, every angle must be smaller than 180°
- Otherwise, the interior angles are useless. At a point, known as theincenter, the bisectors of each of the three internal angles come together
- This point also happens to be located at the center of the triangle’s incircle.

### Note

The inner angles of a triangle only add up to 180° when the triangle is planar, which means it is laying on a flat surface such as a table. If the triangle is not planar, for example, if it is resting on the curved surface of a sphere, the angles do not add up to 180° as they would otherwise.

## Other triangle topics

- Defining a triangle, the hypotenuse of the triangle, triangle inner angles, triangle external angles, triangle exterior angle theorem, Pythagorean Theorem, and Proof of the Pythagorean Theorem pythagorean triples
- A triangle’s circumcircle and incircle
- A triangle’s medians and altitudes
- The mid-section of a triangle
- The Triangle inequality
- The side / angle relationship

### Perimeter / Area

- A triangle’s perimeter
- A triangle’s surface area
- A triangle’s circumference Heron’s formula is as follows: The area of an equilateral triangle
- The area calculated using the “side angle side” technique
- The area calculated using the “side angle side” method
- A triangle’s surface area when the triangle’s perimeter is set

### Triangle types

- Obtuse triangle
- Acute triangle
- Right triangle
- Isosceles triangle
- Scalene triangle
- Equilateral triangle
- Equiangular triangle
- Isosceles trigonometry 3-4-5 triangle
- 30-60-90 triangle
- 45-45-90 triangle
- 3-4-5 triangle

### Triangle centers

- A triangle’s orthocenter is located at the intersection of the circumcenter and the incenter. a triangle’s incenter is located at the intersection of the circumcenter and the incenter.

### Congruence and Similarity

- Quiz of the triangle kind
- Problem with the Ball Box
- How many triangles are there? Orbits of satellites

(C) 2011 Copyright Math Open Reference. All rights reserved. All intellectual property rights are retained.

## Interior Angles of a transversal definition

When atransversal crosses two (typically parallel) lines, a transversal is formed. Each pair of inner angles is contained inside the parallel lines and is on the same side of the transversal as the previous pair. Consider the following: A or B can be selected by dragging an orange dot. It is important to note that the two interior angles given are supplementary (they add up to 180°) if the lines PQ and RS are parallel to one another. If we look at the diagram above, the transversalAB crosses the two lines PQ and RS, resulting in the creation of junctions at E and F, respectively.

As a result, there are two pairs of these angles.

Keep in mind that interior refers to the area between the parallel lines.

## The parallel case

If the transversal runs over parallel lines (which is the most common scenario), then the interior angles are additional (they add up to 180°) to the transversal.

As a result, if you change points A or B in the diagram above, the two internal angles represented always sum up to 180°. Try it out and see if you can persuade yourself that this is real. To explore both pairs of interior angles in succession, select ‘Other angle pair’ from the drop-down menu.

## The non-parallel case

The internal angles of the transversalcuts still add up to a constant angle, but the sum is not 180° if the transversal slices over lines that are not parallel. Drag point P or Q to the left or right to make the lines nonparallel. As you move A or B, you will see that the interiorangles add up to a constant, but that the sum does not equal 180° as expected. (Please keep in mind that the angles have been rounded to the closest degree for clarity, so keep that in mind while checking this.)

## Other parallel topics

- Equivalent interior and exterior angles
- Corresponding interior and exterior triangles
- Transversal triangles and transversal triangles
- Interior and exterior triangles and transversal triangles and transversal triangles.

(C) 2011 Copyright Math Open Reference. All rights reserved. All intellectual property rights are retained.

## Triangle Interior Exterior Angles – Maple Help

Triangles are made up of two angles: the inside angle and the outside angle.

Main Concept |

Aninterior angleof a polygon is formed by two sides of a polygon that share an endpoint. A shape has one internal angle per vertex . For atriangle, an interior angle is the angle between any two of the triangle’s three sides.Anexterior angleof a polygon is any of the angles formed by the intersection of one of the polygon’s sides with a line extended from an adjacent side.Properties:- The sum of the interior angles of a triangle is equal to 180 degrees.- The sum of the exterior angles of a triangle is equal to 360 degrees. |

Instructions | |

The plot below shows a visual representation of the properties mentioned above, namely that the interior and exterior angles of the triangle add to 180 and 360 degrees respectively.Choose either interior angles or exterior angles. Drag the red point to change the angles of the triangle and move the slider from left to right to see the proofs in motion.Interior Angles:The interior angles form a semi-circle (180 degrees).Exterior Angles:The exterior angles form a full circle (360 degrees). |

The following slide will animate the proof:

## Co-interior angles

In this section, we will study about co-interior angles, including how to recognize co-interior angles, and we will use our newfound knowledge to problem solving. There are also angles in parallel lines worksheets that are based on Edexcel, AQA, and OCR exam questions, as well as further suggestions on where to go next if you’re still having trouble with the problem.

## What are co-interior angles?

When two parallel lines are crossed by a transversal, co-interior angles are formed in the space between them. A transversal has two angles that occur on the same side of it, and the sum of these angles is always 180o. When you add up the co-interior angles, the sum is 180og plus 180i + j = 180k + l = 180m + n = 180og. By sketching a C shape, we can frequently identify co-interior angles. Only when both internal angles are 90 degrees are the two interior angles equal. The co-interior angles may be calculated in all other circumstances by subtracting one from the other and dividing the result by 180o.

### What are co-interior angles?

In order to determine a missing angle between two parallel lines, do the following:

- Draw attention to the angle(s) that you are already familiar with. In order to locate a missing angle in the diagram, state the alternative angle, co-interior angle, or matching angle fact. In order to compute the missing angle, use fundamental angle facts.

Steps 2 and 3 can be completed in any sequence, and they may need to be repeated a few times. Step 3 may or may not be necessary in all cases.

### Explain how to calculate with co-interior angles

Get your free co-interior angles worksheet, which includes more than 20 problems and answers, by clicking here. There are both logic and application problems in this section. TO BE ANNOUNCED SOONX

### Co-interior angles worksheet

Get your free co-interior angles worksheet, which includes more than 20 problems and answers, by clicking here. There are both logic and application problems in this section. TO BE ANNOUNCED SOON

## Angles in parallel lines – co-interior angles examples

Calculate the size of the omitted angle by using the formula. Please provide justification for your response. 2 Co-interior angles can be used to locate a missing angle. The co-interior angle on the figure can be labeled as 60o in this case since 120 + 60 = 180o. 3 To determine the missing angle, start with a fundamental angle fact. Because is vertically opposite 60o in this case, = 60o.

### Example 2:co-interior angles

Calculate the size of the omitted angle by using the formula. Please provide justification for your response. Draw attention to the angle(s) that you are already familiar with. We may utilize either the 118o angle or the 83o angle in this situation. The 118o angle will be used in this example since it investigates an alternate way that has not yet been presented. Co-interior angles can be used to locate a missing angle. Co-interior angles add up to 180 degrees, therefore 180 118 = 180 degrees, and the missing angle marked is 62 degrees.

We have a trapezium with the sum of internal angles equal to 360o in this case.

Using this information, we can determine the value of: [begintheta =360 -left(118 +62 +83 -right) -endtheta =97] [begintheta =360 -left(118 +62 +83 -right) -endtheta =97] [begintheta =360 -left(118 +62 +83 -right) [begintheta =97] [begintheta

### Example 3: co-interior angles with algebra

Calculate the size of the omitted angle by using the formula. Please provide justification for your response. Draw attention to the angle(s) that you are already familiar with. First and foremost, we must determine the value of x. Co-interior angles can be used to locate a missing angle. Because 11x and 4x are co-interiors, we may declare that [begin11x+4x =180][begin11x+4x =180] [[15x =180x =12]] [[15x =180x =12]] [[15x =180x =12]] As a result, we have two co-interior angles of 11x = 132o and 4x = 48o, respectively.

Because the sum of the angles in a triangle is 180 degrees, the angles in the triangle are 48 degrees and 90 degrees.

Because theta and 42 are on a straight line, [begintheta =180-42 theta =138] and [endtheta =180-42 ] are equivalent.

### Common misconceptions

Because there are so many angle facts, it’s easy to confuse alternate angles with matching angles when learning them. To avoid this from happening, think of co-interior angles as being located within the C shape’s boundaries. Angles are measured with the use of a protractor. Most diagrams are not to scale, and hence employing a protractor will not result in a correct answer unless it is by chance that you get it right. Co-interior angles are one of a series of courses designed to assist students in their revision of angles in parallel lines.

The following are some of the other lessons in this series:

- Intersecting angles between parallel lines
- Corresponding angles
- Alternating angles

### Practice co-interior angles questions

Theta and 44 are co-interior angles in the triangle. As a result, theta = 180-44=136 is obtained. In order to calculate 180-125=55, we must use co-interior angles. Using co-interior angles once more, we can see that theta=180-55=125 is a valid value. Using co-interior angles, we can get 180-110=70° using co-interior angles. The opposite angle at the bottom of the triangle, which is also 70 degrees since it is an isosceles triangle, is also 70 degrees. Then, considering the angles of a triangle, theta=180-(70+70)=40, which is equal to 40.

Because (theta+68) and 68 are co-interior angles, (theta+68) + 68 = 100theta = 180-(68+68)theta=44degree42and38degree30and30degree80 and100degree78 and102degree42and38degree80 and100degree78 and102degree The angles 3x+12 and 2x+18 are co-interior angles, and as a result, they sum up to 180 degrees.

### Co-interior angles GCSE questions

1.(a) Determine the length of anglex. (b)Determine the length of angley. (3 points)Show answer(a)180-38=142 as co-interior angles add to180 180-142=38 as angles on a straight line add to180 180-142=38 as angles on a straight line add to180 (2) (b)180 –=32 is the answer (1) 2. Calculate the value of x in terms of a. (3 points)Exhibit your response 5x – 7 + 3x + 11 = 180 (1) 8x + 4 = 180 (1) x=22 5x – 7 + 3x + 11 = 180 (1) 3. Are the linesABandCD parallel to one another? Give a justification for your response.

(1) In the case of two parallel lines, the co-interior angles sum up to 180 degrees (1)

## Learning checklist:

You have now learnt how to do the following:

- Use the characteristics of angles at a point, angles at a point on a straight line, and vertically opposed angles to solve your problems. Realize and apply the link between parallel lines and alternating, matching angles

## Still stuck?

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