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

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

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

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

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

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

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