In this video you will learn the correct steps for using perpendicular lines to prove angles congruent in a logic proof.

Perpendicular lines form right angles at the location of intersection.

In the example in the video we are given the information that \overline{AC}\perp\overline{BD}, so mark the right angles in the diagram. On the statement-reason proof chart, write down the given information.

Now, we know that \angle ACB and \angle ACD are right angles because perpendicular lines form right angles. Since they are both right angles, we can then say that \angle ACB \cong \angle ACD because all right angles are congruent.

With only a small piece of information, \overline{AC} \perp \overline{BD}, we found that \angle ACB \cong \angle ACD.