Britton rotated trapezoid ABCD 180 degrees on the coordinate pleane. If angle B is 20 degrees and angle D is 90 degrees, what is the degree measurement of angle B'?

Given:

Trapezoid ABCD rotated 180 degrees to get the trapezoid A'B'C'D'.

To find:

The measure of angle B'.

Solution:

We know that, rotation is a rigid transformation. It means the size and shape of the figure remains same after rotation or be can say that image and preimage are congruent.

So, .

                 (CPCTC)

Therefore, the measure of angle B' is 20 degrees.