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interior angle

 
Dictionary: interior angle
interior angle
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interior angle

Angles 3, 4, 5, and 6 are interior angles; angles 3,6 and 4,5 are alternate interior angles.
(Academy Artworks)

n.
  1. Any of the four angles formed between two straight lines intersected by a third straight line.
  2. The angle formed inside a polygon by two adjacent sides.

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WordNet: interior angle
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Note: click on a word meaning below to see its connections and related words.

The noun has one meaning:

Meaning #1: the angle inside two adjacent sides of a polygon
  Synonym: internal angle


Wikipedia: Internal and external angle
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Internal and External angles

In geometry, an interior angle (or internal angle) is an angle formed by two sides of a simple polygon that share an endpoint in. This angle must be an angle on the inner side of the polygon to be an internal angle. A simple polygon has exactly one internal angle per vertex.

If every internal angle of a polygon is less than 180°, the polygon is called convex.

In contrast, an exterior angle (or external angle) is an angle formed by one side of a simple polygon and a line extended from an adjacent side.

The sum of the internal angle and the external angle on the same vertex is 180°.

For example: x+35+75=180
x+110=180
x+110-110=180-110
x=70

The sum of all the internal angles of a Regular polygon can be determined by 180(n-2) where n is the number of sides. A pentagon's internal angles add up to of 540 degrees (shown below)
180(n − 2) = 180(5 − 2) = 180(3) = 540
Knowing this you can easily find the measure of each angle (assuming those angles are part of a regular polygon) with
\frac{180(n-2)}{n}.
So continuing from the above example with the pentagon...
\frac{540}{n}=\frac{540}{5}=108

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Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.  Read more
WordNet. WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Internal and external angle" Read more