Question

In the given figure

If $l\parallel m$ then $\angle 3=\_\_\_\_$

Answer 1

If two lines are parallel and cut by a transversal then corresponding angles are equal.

$\angle 4$ is corresponding to $\angle 3$ and are equal as as line $l\parallel m$.

When two parallel lines are cut by a transversal then alternate interior angles are equal.

$\angle 5$ and $\angle 3$ are alternate and equal .

Hence, If $l\parallel m$ then $\angle 3=\angle 4$ and $\angle 5$