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geometry junior
Problem
What is the degree measure of angle when polygon is a regular hexagon? 
Solution
The sum of the interior angles of an -sided polygon is . For a regular hexagon, the interior angles sum to , so each interior angle has a measure of . Since and are congruent sides of a regular hexagon, is an isosceles triangle. The two base angles are congruent and sum to a degree measure of , so each base angle has a measure of . There are now a couple approaches to finishing the problem.
: We use the fact that trapezoid is an isosceles trapezoid to solve for and . Since and are congruent sides of a regular hexagon, trapezoid is an isosceles trapezoid and the base angles are equal. So we know that . Since the interior angle of a hexagon is and , we know that is a right angle. The acute angles of a right triangle sum to , so . Now we can solve for with , which yields . The degree measure of is .
: We use the fact that trapezoid is an isosceles trapezoid to solve for . Since and are congruent sides of a regular hexagon, trapezoid is an isosceles trapezoid and the base angles are equal. The interior angles of a trapezoid sum to , so we have , which yields . Angle is an interior angle of a hexagon that measure , so . We found that , so . The degree measure of is .
: We use the fact that trapezoid is an isosceles trapezoid to solve for and . Since and are congruent sides of a regular hexagon, trapezoid is an isosceles trapezoid and the base angles are equal. So we know that . Since the interior angle of a hexagon is and , we know that is a right angle. The acute angles of a right triangle sum to , so . Now we can solve for with , which yields . The degree measure of is .
: We use the fact that trapezoid is an isosceles trapezoid to solve for . Since and are congruent sides of a regular hexagon, trapezoid is an isosceles trapezoid and the base angles are equal. The interior angles of a trapezoid sum to , so we have , which yields . Angle is an interior angle of a hexagon that measure , so . We found that , so . The degree measure of is .
Final answer
30^\circ