What's the interior angle of a 5 sided polygon
The exterior angle of a regular n-sided polygon is 360°/n so the interior angle is 180°-360°/n
When n = 5 the interior angle is therefore 180°-360°/5 = 108°
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Here's a pentagon, a 5-sided polygon. From vertex A we can draw two diagonals which separates the pentagon into three triangles. We multiply 3 times 180 degrees to find the sum of all the interior angles of a pentagon, which is 540 degrees.
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