Chapter 2.7, Problem 11PSB

To determine

To prove : $\angle 1$ is supplementary to $\angle 3$ is to be proved

Explanation of Solution

Given information : The following information has been given

  $\angle 1=\angle 2$

Formula used : If A and B are congruent angles, then supplementary of A and B are same angles

Proof : We know that $\angle 2+\angle 3$ form a straight line

Thus, we can say that $\angle 2$ and $\angle 3$ are supplementary angles

Now, we are given that $\angle 1=\angle 2$ . Hence, we can say that supplementary of $\angle 2$ and $\angle 1$ are same angles

Thus, we can say that $\angle 1$ and $\angle 3$ are supplementary angles

Hence, required angles are proved