Question

what is an angle that is supplementary to ∠1?

Explanation:

Step1: Recall supplementary - angle definition

Two angles are supplementary if their sum is 180 degrees.

Step2: Identify the supplementary angle

From the figure, ∠1 and ∠3 form a linear - pair. A linear - pair of angles is supplementary. So the angle supplementary to ∠1 is ∠3.

Answer:

∠3