3.2 Properties of Parallel Lines• Corresponding Angles Postulate – Postulate 3.1

– If a transversal intersects two parallel lines, then corresponding angles are CONGRUENT!!

1 5 2 6

4 8 3 7

Identifying Congruent Angles• Which angles measure 55? How do you know?

• The measure of angle 7 = 55° - Corresponding Angles Postulate.

• The measure of angle 1 = 55° - Vertical Angles Theorem.

• The measure of angle 5 = 55° - Corresponding Angles Postulate because angle 1 and angle 5 are corresponding angles.

Alternate Interior Angles Theorem• If a transversal intersects two parallel lines,

then alternate interior angles are congruent.

3 5 4 6

Same-Side Interior Angles Theorem• If a transversal intersects two parallel lines,

then same-side interior angles are supplementary.

4 5 180m m 3 6 180m m

Alternate Exterior Angles Theorem• If a transversal intersects two parallel lines,

then alternate exterior angles are congruent.

1 7 2 8

Finding Measures of Angles• What are the measures of the missing angles?

3 105m

4 105 180m 4 75m

Finding an Angle Measure• What is the value of y?

( 40) 80 180y 120 180y 60y

More Practice!!!!!

• Homework – Textbook p. 153 - 154 #7 – 20 all!