1. Parallel and Perpendicular Lines
Chapter 3
Parallel and Perpendicular Lines

2. Section 2 Theorems about Perpendicular Lines

3. The Geo-Activity above suggests the following theorems about perpendicular lines.

5. Example 1: Perpendicular Lines and Reasoning
In the diagram, r ⊥ s and r ⊥ t. Determine whether enough information is given to conclude that the statement is true. Explain your reasoning.
<3 ≅ < 5
<4 ≅ <5
<2 ≅ <3

6. Checkpoint: Perpendicular Lines and Reasoning
In the diagram, g ⊥ e and g ⊥ f. Determine whether enough information is given to conclude that the statement is true. Explain.
<6 ≅ < <7 ≅ <10
<6 ≅ < <7 ≅ <11
5. <7 ≅ < <6 ≅ <11

8. Example 2: Use Theorems About Perpendicular Lines In the helicopter at the right, are <AXB and <CXB right angles? Explain.

9. Example 3: Use Algebra with Perpendicular Lines In the diagram at the right, EF ⊥ EH and m<GEH = 30°. Find the value of y.

10. Checkpoint: Use Algebra with Perpendicular Lines Find the value of the variable. Explain your reasoning.