Answer:
. In other words, these two angles are both right angles, and this parallelogram would be a rectangle.
Step-by-step explanation:
Two angles that congruent have the same size.
At the same time, those two adjacent angles of this parallelogram would be a pair of consecutive interior angles. Because the two sides of a parallelogram are parallel to one another, the sum of these two consecutive interior angles would be - they are supplementary to one another.
Let the two angles be and .
because the two angles are congruent.
because these two angles are adjacent angles of a parallelogram.
Hence, .