The initial starting value is 3, and the interior angles of a triangle is formula_16 degrees. Assume that the interior angles of a formula_1-sided polygon is formula_15 degrees. Add on a triangle which makes the figure a formula_5-sided polygon, and that increases the count of the angles by 180 degrees formula_20 degrees. Since both the base case and the inductive case are handled, the proof is now complete.
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