Chapter 4, Problem 12CUR

To determine

To Find: which line is parallel to each other in the given figure if $m\angle 8+m\angle 9=180$ .

Answer to Problem 12CUR

  $c\parallel d$

Explanation of Solution

Given

  

And $m\angle 8+m\angle 9=180$ .

Calculation:

Using theorem which states-

If two lines are cut by a transversal and same-side interior angles are supplementary, then the lines are parallel.

Since, angle $\angle 8$ and $\angle 9$ are same interior angles on same side formed by line $a$ , which is the transversal line given their sum is $180°$ , by theorem, $c\parallel d$ .

Therefore, answer is $c\parallel d$