Find the corners of a rectangular trapezoid if one of its corners is 20 degrees.

Given:

ABCE – rectangular trapezoid,

angle E = 20 degrees.

Find the degree measures of the angles of the parallelogram ABCE: angle B, angle C, angle A -?

Solution:

Consider a rectangular trapezoid ABCE. It has two straight angles, then angle A = angle B = 90 degrees.

We know that the sum of the degree measures of a quadrilateral is 360 degrees. Consequently:

angle A + angle B + angle E + angle C = 360;

90 + 90 + angle E + 20 = 360;

180 + angle E + 20 = 360;

200 + angle E = 360;

angle E = 360 – 200;

angle E = 160.

Answer: 90 degrees; 160 degrees; 90 degrees.