Exterior angles Chapter 5 (p. 225)
Angles that form linear pairs with the interior angles of a polygon
In geometry, an exterior angle of a polygon is an angle that is formed by a side of the polygon and an adjacent side that is extended beyond the polygon.
The exterior angle theorem states that the measure of an exterior angle of a triangle is equal to the sum of the measures of the two non-adjacent interior angles of the triangle. In other words, if angle A is an exterior angle of triangle ABC, then angle A = angle B + angle C.
This theorem can be used to solve various problems involving triangles, such as finding the measure of an unknown angle or verifying the congruence of two triangles.
It is important to note that the sum of the exterior angles of any polygon is always 360 degrees. Therefore, if you know the measure of one exterior angle of a polygon, you can easily find the measure of the remaining exterior angles by dividing 360 degrees by the number of sides of the polygon.
In summary, exterior angles play an important role in the study of geometry, particularly in the analysis of polygons and triangles.
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