1. 3.2 Proofs and Perpendicular Lines
CAS 2, 4
Goal 1: Write different types of proofs
Goal 2: Prove results about perpendicular lines.
3.2 Proofs and Perpendicular Lines

2. Flow Proof
A flow proof uses arrows to show the flow of the logical argument.
Each reason in a flow proof is written below the statement it justifies

3. Ex. 1 Write a Flow Proof
Given: AB= CD
Prove: AC=BD

4. Theorems about Perpendicular Lines
Thm 3.1
If two lines intersect to form a linear pair of congruent angles, then the lines are perpendicular B D A C

5. Theorems about Perpendicular Lines (continued)
Thm 3.2
If two sides of two adjacent acute angles are perpendicular, then the angles are complementary

6. Theorems about Perpendicular Lines (continued)
Thm 3.3
If two lines are perpendicular, then they intersect to form four right angles.

7. Ex. 2 Write a proof of the Congruent Supplements Theorem
Step 1: Go back to page 111 ( or your notes) and read that theorem.
Decide what you are given
Decide what you are to prove.

8. Ex. 2 Write a proof of the Congruent Supplements Theorem (continued)
Given: Two angles are supplementary to the same angle
Prove: then they (the two angles) are congruent.
Make a sketch and identify the angles.

9. Ex. 2 Write a proof of the Congruent Supplements Theorem (continued)
Given:
Prove: