1. Proofs & Perpendicular Lines Sec. 3.2 p. 136
GOALS:
To learn the characteristics of three different types of proofs
To write a paragraph proof
To learn theorems on perpendicular lines

2. Theorems 3.1 & 3.2
Theorem 3.1 g h
Theorem 3.2 1 2

3. Theorem 3.3
Theorem 3.3
If two lines are perpendicular, then they intersect to form four right angles. m l

4. Examples
Which theorem or postulate justifies the following given that the lines are perpendicular? 1) 6 5 m 2) 3 4 l

5. Two-Column Proof of Theorem 3.2A
Given:
Prove: 2 1 B C
Statements Reasons

6. Three types of Proofs & Characteristics
Two column proof:
Most formal
Lists numbered statements in left column and a reason for each statement in the right column
Paragraph proof:
Describes the logical argument with sentences
More conversational
Flow proof:
Uses the same statements and reasons as a two-column proof, but the logical flow connecting the statements is indicated by arrows

7. See notes sheet for an example of the three types of proofs!