Download Geometry B Date: ______ 3.3 Proving Lines Parallel Objective: To

Geometry B
Date: _____________
3.3 Proving Lines Parallel
Objective: To use the angles formed by a transversal to prove two lines are parallel
Recall:
 Conditional: ____________________________________________________________

Converse: ______________________________________________________________
Last time, we said “If two lines are parallel, then the corresponding angles are equal.”
The converse states: _____________________________________________________________
Ex. 1: Converse of the Corresponding Angles Postulate
Tell whether the two lines are parallel based on the given information. If they are, explain why and write
a statement to show that they are parallel.
a. 4  8
b. 1  5
c. m3  4x  80 , m7  3x  50 , x  30
d. m2  4x  25 , m6  5x  12 , x  13
The other angle pair theorems have converses that are true as well. Write the converse of each statement
(Remember: Converse means flip)
Alternate Interior Angles: If two lines are parallel, then the alternative interior angles are congruent.
Converse: ___________________________________________________________________________
Alternate Exterior Angles: If two lines are parallel, then the alternate exterior angles are congruent.
Converse: ___________________________________________________________________________
Consecutive Interior Angles: If two lines are parallel, then the consecutive interior angles are
supplementary.
Converse: __________________________________________________________________________
Ex. 2: Using the Converse of the Other Angle Postulates
Tell whether the two lines are parallel based on the given information. If they are, explain why and write
a statement to show that they are parallel.
a. 4  8
b. 7  3
c. m2  10x  8 , m3  25x  3 , x  5
d. m1  2x , mx  50 , x  50
HW: 3.3 Worksheet