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Home > CCG > Chapter 4 > Lesson 4.2.5 > Problem 4-115

4-115.

Two decreasing parallel lines are cut by two transversals. At the intersection of the left parallel line & the top transversal, the interior right angle is, theta.  About the right parallel line & the top transversal, the exterior right angle is, 112 degrees.  About the left parallel line & the bottom transversal, the interior right angle is, 85 degrees.  About the right parallel line & the bottom transversal, the exterior right angle is, alpha.Find the values of and in the diagram at right. State the relationships you used.  

There are several correct methods.

The value of can be found by using corresponding and supplementary angles.

Label added at the intersection of the left parallel line & the top transversal, on the exterior right angle, 112 degrees, with arrow pointing from corresponding 112 degree angle.

Label added to angle labeled theta, 68 degrees.

The value of can be found using corresponding angles.

Label added to angle labeled alpha, 85 degrees, with arrow pointing from corresponding 85 degree angle.