5.2

Proving that Lines are Parallel

ACD is an exterior angle. A & B are remote interior angles.mACD is greater than mA.mACD is greater than mB

DCB

A

1 24

8765

3

1. 1 22. PQ ║ RS3. PQR RSP4. 3 45. QR ║ PS6. PQRS is a

parallelogram.

1. Given2. Alt. int. s → ║ lines.3. Given4. Subtraction Property.5. Same as 2.6. A 4-sided figure with both pairs

of opposite sides parallel is a parallelogram.

7 ways to prove lines parallel• AIP Alt Interior Angles ≅

•CAP Corresponding Angles ≅

•AEP Alt Ext Angles ≅

•SSISP same side interior angles supp parallel lines

•SSESP same side exterior angles supp parallel lines

•2p3p two lines in a plane are both perpendicular to the same line they are parallel

•Transversal of parallel if 2 lines are both parallel to the same line then they are parallel