Proving Lines Parallel Lesson Proving Lines Parallel Lesson : Proving Lines Parallel

Conditional Statement Definition: A conditional statement is a statement that can be written in if-then form. “If _____________, then ______________.” Example: If your feet smell and your nose runs, then you're built upside down. Continued……

Conditional Statement - continued Conditional Statements have two parts: The hypothesis is the part of a conditional statement that follows “if” (when written in if-then form.) The hypothesis is the given information, or the condition. The conclusion is the part of an if-then statement that follows “then” (when written in if-then form.) The conclusion is the result of the given information.

Forms of Conditional Statements Converse: Switch the hypothesis and conclusion If two angles are vertical, then they are congruent. If two angles are congruent, then they are vertical. Continued…..

Ways to Prove Two Lines Parallel Show that corresponding angles are equal (Corresponding Angles Converse) Show that alternative interior angles are equal (Alternate Interior Angles Converse) Show that consecutive interior angles are supplementary (Consecutive Interior Angles Converse) Show that alternative exterior angles are equal (Alternate Exterior Angles Converse)

What does it mean? If then

Biconditional When a conditional statement and its converse are both true, the two statements may be combined. Use the phrase if and only if (sometimes abbreviated: iff) Statement: If an angle is right then it has a measure of 90. Converse: If an angle measures 90, then it is a right angle. Biconditional: An angle is right if and only if it measures 90.

Examples: Proving Lines Parallel Find the value of x which will make lines a and lines b parallel. 2. 1. 3. 4. Answers: 1. 20° 2. 50° 3. 90° 4. 20°

Example

Homework Pg. 165 #5, 17, 19, 20, 21, 26 Pg. 168 #34, 40, 42, 44