1. 8-3 Angle Relationships Objective: Students identify parallel and perpendicular lines and the angles formed by a transversal.

2. Vocabulary  Adjacent angles- have a common vertex and a common side, but no common interior points.  Vertical angles- are the nonadjacent angles formed by two intersecting lines.  Transversal- is a line that intersects two or more lines that lie in the same plane. 4 1 3 2 4 1 3 2

3. Example 1  If m ∠2 = 75°, find m∠4 Finding Angle Measures 4 1 3 2  Use the diagram to find each angle measure.  If m ∠3 = x °, find m∠1

4. Transversals  If two parallel lines are intersected by a transversal,  corresponding angles are congruent,  alternate interior angles are congruent,  and alternate exterior angles are congruent.  If the transversal is perpendicular to the parallel lines, all of the angles formed are congruent 90° angles. Corresponding angles Alternate interior angles Alternate exterior angles

5. Example 2  In the figure, line a ll line b. Find the measure of each angle. Finding Angle Measures of Parallel Lines Cut by Transversals a b c 3 1 7 6 4 5 2

6. Guided Practice  Page 390  Problems 1-2