# Sum of interior angles

Find the sum of the interior angle of:pentagon,15-gon,and 18-gon.

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#### Solution Preview

In general the sum of the interior angle of a closed shape with m sides (a "m-gon") is equal to 180*(m-2). Because by drawing lines from a corner to all the non-adjacent corners we can draw exactly (m-2) triangles inside the "m-gon", such that the total sum of the sum of interior angles of all triangles will ...

#### Solution Summary

This shows how to find the sum of interior angles of various polygons. The interior angles of pentagons are examined.

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