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Name
3-3
Class
Date
Think About a Plan
Proving Lines Parallel
Algebra Determine the value of x for which r ║ s.
Then find m1 and m2.
Given: m1 = 20  8x, m2 = 30  16x
1. Is 1 an interior angle or an exterior angle? Is 2 an interior
angle or an exterior angle?
<1
is exterior and <2 is interior
2. Do 1 and 2 lie on the same side of the transversal or on opposite sides of
the transversal?
Same Side
3. What type of angle pair are 1 and 2?
Corresponding
4. If r ║ s, and 1 and 2 are the type of angle pair you named above, how are
the angles related?
congruent
5. What equation can you write using the given information? 20-8x=30-16x
6. What is the value of x? x=10/8 or 5/4
7. Substitute the value of x into each expression. What are the measures of each
angle? 20-8(5/4)=20-10=10
m1 = 20  8x =
m2 = 30  16x =
30-16(5/4)=30-20+10
8. Would this value of x prove that r ║ s? Explain. Yes, by the converse of the corresponding angle
theorem/postulate
Prentice Hall Geometry • Teaching Resources
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