Question

Line AB is parallel to line CD. What is the measure of 21?1/2A— В3/45 80°C→D78

Answer 1

The final answer is 100 degrees (Option 2)

We are required to find angle <1.

In order to do this, there are some theorems about angles we need to consider.

$<4+80^0=180^0\text{ (Consecutive Interior Angles add up to 180)}$

Now, we can easily solve for < 4:

$\begin{gathered} <4+80^0=180^0 \\ \text{subtract 80 from both sides} \\ <4+80^0-80^0=180^0-80^0 \\ \\ \therefore<4=100^0 \end{gathered}$

Now that we know <4, we can relate <4 with <1 that we are required to find.

The relationship is given below:

$<1=<4\text{ (Vertically Opposite Angles are equal)}$

Thus, we can conclude that:

if < 4 = 100, and < 1 = < 4

Therefore,

<1 = 100 degrees.

The final answer is 100 degrees (Option 2)