Answer:
128.57°
Step-by-step explanation:
A regular heptagon is a 7-sided polygon whose 7 interior angles all have the same measure. The measure of each of them in degrees can be computed from the formula
interior angle measure = 180(n-2)/n . . . where n = 7 is the number of sides
interior angle measure = 180(5/7) = 128 4/7 ≈ 128.57
The measure of one interior angle of a regular heptagon is about 128.57°.
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The polygon does not have to be regular to find an interior angle. It needs to be of such a nature that the interior angles are known from the description of the polygon. For example, an isosceles right triangle is not a regular polygon, but you know that the measure of one acute angle is 45°.