Download Geometry 3-3

Warm-Up
x+2
3x - 6
What is the value of x?
Geometry 3-3
Proving Lines Parallel
Example: Using the Converse of the Corresponding
Angles Postulate
Use the Converse of the Corresponding Angles
Postulate and the given information to show
that ℓ || m.
m3 = (4x – 80)°,
m7 = (3x – 50)°, x = 30
• Converse of the Alternate Interior Angle
Theorem:
If two alternate interior angles are congruent,
then the lines are parallel.
• Converse of the Alternate Exterior Angle
Theorem:
If two alternate exterior angles are congruent,
then the lines are parallel.
• Converse of the Same Side Interior Angle
Theorem:
If two same side interior angles sum up to
180°, then the lines are parallel.
Example 2: Determining Whether Lines are Parallel
Show that r || s.
m2 = (10x + 8)°,
m3 = (25x – 3)°, x = 5