Brian McCall

**Univ. of Wisconsin**

J.D. Univ. of Wisconsin Law school

Brian was a geometry teacher through the Teach for America program and started the geometry program at his school

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You can determine properties of two angles by using properties of corresponding angles. Remember, corresponding angles are congruent. So, by using corresponding angles, you can determine that two angles are congruent. Additionally, two angles that are adjacent are linear are supplementary (meaning that the sum of their measures is 180°. By using properties of corresponding angles, you can find that an angle around one line is supplementary to an angle on another line.

In this problem you’re being asked to take what you know about corresponding angles and apply it to a problem where you’re not necessarily looking for a number. It asks what must be true about x and y?

Let’s start by figuring out what could this angle be. Well it corresponds with x. We have two parallel lines and I know that because we have double arrows on both on both of them, so that means that this angle right here must be x.

Since x and y are adjacent and linear, then these two must be supplementary so what must be true? I’m going to write they are supplementary. So we used what we knew about corresponding angles and what we knew about linear pairs of angles.