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# Corresponding Angles - Problem 3

###### Brian McCall

###### 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

Remember that angles that are adjacent and linear must add up to 180°. Using this, you can determine the measure of an unknown angle if you know the measurement of the other angle(s) on that line. Additionally, recall that vertical angles, a pair of angles on opposite sides of a shared vertex, are congruent. Another fact to remember is the Triangle Angle Sum Theorem, which states that the sum of the measures of the angles in a triangle is 180°. Using these facts, you can determine the measurements of various angles in a diagram involving parallel lines and two intersecting transversals.

Now that you know about corresponding angles, you’re going to have to apply it to a situation, something like this, on a homework or a quiz. What you have to do here is take what you know, what you’re given and find the missing angles.

So I always start with well I know I have 80 degrees, I know I have two parallel lines and I have two transversals, so 80 corresponds to x. Since they’re corresponding angles, x must be 80 degrees, so I’m going to erase x and I’m going to write 80 degrees and I can come over here where I’m writing my answer and I’m going to write that x is 80 degrees.

So now that we found x, we need to find y and we need to find z. Well I can use what I know about these 3 angles being on a line and that they have to add up to 180 degrees. 80 plus 40 is 120 which means y has to be 60 if they sum to 180 degrees, so 60 degrees for y and last we have angle z. Now there’s a couple of ways that you can find angle z and I’ll show you a way that you’ve probably not seen. 40 degrees is a vertical angle with this angle right here. Vertical angles are always congruent. 40 degrees is corresponding to z, so that means that z must be 40 degrees.

So I’m going to come over here and I’m going to write that z must be 40 degrees. The key to angle cases use what you know. You probably are going to use some vertical angles, maybe a linear sum conjuncture and you’ll solve it pretty quickly.

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###### Brian McCall

B.S. in Chemical Engineering, University of Wisconsin

J.D. University of Wisconsin Law School (magna cum laude)

He doesn't beat around the bush. His straightforward teaching style is effective and his subtle midwestern accent is engaging. There's never a dull moment with him.

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