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Home > CC4 > Chapter 1 > Lesson 1.2.1 > Problem 1-42


Recall what you learned about angle relationships in previous courses. (See the Math Notes box in this lesson if you need a reminder.) Determine the measures of the labeled angles. The double arrowheads indicate that the pair of lines is parallel. Homework Help ✎

All three of these can be solved using multiple techniques related to parallel lines.




  • a: Corresponding angle with 123°, so ma = 123°.
    b: ∠a and ∠b are vertical angles, so they have equal measures. Therefore, mb = 123°.
    c: ∠c and 123° form a pair of supplementary angles, so mc = 57°.

    f and 82° form a pair of supplementary angles. How are ∠e and ∠f related?

    Since there are parallel lines, look for relationships between pairs of angles such as alternate interior, corresponding, or same-side interior.