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View Full Version : What is the sum of the formulas of exterior and interior angles of polygon


kris12345
Mar 18, 2013, 03:04 PM
For a geometry test they asked for the sum of the exterior and interior angle formulas then asked what the sum represented. You have to use a n-gon. I want to make sure I'm right.

What I think it is:

Exterior- 360/n
Interior- (n-2)180/n

Sum- (n-2)540/2n

The sum is one interior and one exterior angle combined.

ebaines
Mar 19, 2013, 06:10 AM
What you have writtem for both the interior and exterior angle formulas are correct only for regular polygons, where all angles are the same. With that caveat you need to check your addition: the sum of the two formulas is


\frac {(n-2)180} n + \frac {360} n = \frac {n180- 2(180)+360} n = 180


If you draw a sketch of a corner of a polygon and note the interior and exterior angles you can see how they add to 180.