Question

Line AB is parallel to line CD. What is the measure of angle 4?

Answer 1

Answer:

100 degrees

Explanation:

From the given figure, we can see that the sum of <5 and 80 degrees will be 180 degrees;

$\begin{gathered} \angle5+80=180\text{ (sum of angles on a straight line)} \\ \angle5=180-80 \\ \therefore\angle5=100^{\circ} \end{gathered}$

We know that alternate interior angles are always equal and we can see from the figure that <5 and <4 are alternate interior angles, so we have that;

$\angle5=\angle4=100^{\circ}$