Hello!

I have a geometry problem from the book "College Geometry: A Discovery's Approach" that is giving me a hard time. It is as follows:

Problem: 4.1 22

Prove that if two angles with respective sides are perpendicular, the angles are either congruent or a supplementary pair.

I managed to solve this problem a long time back but I forgot how to do it -_-.

Anyone who can solve this?