The polygon below is a regular octagon
Calculate the sides of the angles x and y.

x = 135     y = 45

Step-by-step explanation:

The sum of the measure of interior angles can be found by equation  

(n - 2) x 180            n is the number of sides

(8 - 2)180 = 1080

Sum of measure of interior angles is 1080 degrees. Variable x, which we are solving for, it the measure of one interior angle. To find x, divide 1080 by 8 to find the measure of one interior angle.

1080 / 8 = 135

x = 135 degrees

We know that a trapezoid like the one formed in the octagon has 2 pairs of congruent angles. we know two of the angles already, as they are the measure of one interior angle, or 135 degrees. The sum of the measure of interior angles of a trapezoid is 360 degrees.

360 - 2(135) = 90

The sum of the remaining two angles of the trapezoid are 90 degrees. These two angles are equal, so divide 90 by 2.

90 / 2 = 45

y = 45 degrees.

expression #3 is not equivalent. the others are.