Back to Prove theorems about lines — Problem 1 · Task Set 9

Exercises: Prove Theorems About Lines and Angles

Work through each section in order. For proof problems, show each step with its justification. Express angle measures in degrees.

Grade 9·21 problems·~35 min·Common Core Math - HS Geometry·standard·hsg-co-c-9

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Warm-Up: Review What You Know

These problems review skills you already know.

Two lines intersect forming four angles. One angle measures $70^\circ$ . Which angle measure could belong to an adjacent angle at the same intersection?

$70^\circ$

$110^\circ$

$140^\circ$

$20^\circ$