Britton rotated trapezoid ABCD 180° on the coordinate plane. If angle B is 20° and angle D is 90°, what is the degree measurement of angle B′? 20°
70°
90°
180°

Given:

Britton rotated trapezoid ABCD 180° on the coordinate plane.

m∠B=20° and m∠D=90°.

To find:

The measure of ∠B'.

Solution:

We know that, rotation is a rigid transformation. It means the size and shape of the image and preimage are same and they are congruent.

Trapezoid ABCD rotated 180° on the coordinate plane to get A'B'C'D'. So, ABCD is congruent to A'B'C'D'.

              (CPCTC)

So, measure of both angles are same.

Therefore, the correct option is A.

i would need to see the dot plot : )