3-1 Properties of Parallel Lines M11.B 2.3.11.A Objectives: To identify angles formed by two lines and a transversal To prove and use properties of parallel lines

Vocabulary A transversal is a line that intersects two coplanar lines at two distinct points. (8 angles are formed) l m t

4 Types of Angles Alternate interior angles Same-side interior angles Corresponding angles Alternate exterior angles 6 5 3 1 2 4 8 7

Example: Identifying Angles Same side Interior Angles Corresponding Angles 1 4 8 5 3 2 6 7

Postulate 3-1: Corresponding Angles If a transversal intersects two parallel lines, then corresponding angles are congruent. Example: t l m

Alternate Interior/Exterior Angles If a transversal intersects two parallel lines, then alternate interior angles and the alternate exterior angles are congruent. t a b

Same Side Interior Angles If a transversal intersects two parallel lines, then same-side interior angles are supplementary. Example:

Find the measure of each missing angle…Justify your answer

Vocabulary - Review Straight Angle – Angle(s) measure 180° to form a straight angle.

Example: Using algebra to find Angle Measures 2x y (y - 50)