Chapter 3.2, Problem 21WE

To determine

To prove: $\angle 1$ is supplementary to $\angle 7$ .

Explanation of Solution

Given information:

Given $k\parallel l$

Given figure

Calculation:

To proof is as follows in the table:

Statement	Reasons
$k\parallel l$	Given
$\angle 4\cong \angle 7$	Vertically opposite angles
$\angle 1$ and $\angle 4$ are supplementary angles	By the definition of supplementary
$\angle 1$ is supplementary to $\angle 7$	By 2 and 3.