Write a formula to find the number of sides n in a regular polygon given that the measure of one interior angle is

Here is the first polygon Sam's teacher assigns: K J H B D G E F Divide the polygon into triangles and use them to find the sum of the interior angles of the polygon.

Find 0 in the triangle Shown velow 2.

For concave pentagon ABCDE, find the measure of the reflex angle at vertex E (in degrees) if  m∠A = m∠D = x°,   m∠B = m∠C = (5x)°,  and the measure of the reflex angle at vertex E is (8x)°. A pentagon has 5 labeled vertices and 5 marked angles. The first side starts at vertex A, goes down and to the left, and ends at vertex B. The second side starts at vertex B, goes down vertically, and ends at vertex C. The third side starts at vertex C, goes down and to the right, and ends at vertex D. The fourth side starts at vertex D, goes up and to the left, and ends at vertex E. The fifth side starts at vertex E, goes up and to the right, and ends at vertex A. ∠A is marked with a single arc. ∠B is marked with a double arc. ∠C is marked with a double arc. ∠D is marked with a single arc. The reflex angle at E is marked with an arrow.