Chapter 2

3.1 Parallel Lines and Transversals

Parallel lines - coplanar lines that don’t intersect 

Skew lines - noncoplanar lines that don’t intersect 

Parallel planes - planes that don’t intersect 

Transversal - a line that intersects 2 or more coplanar lines at 2 different points 

Can’t be at intersection points 

Corresponding angles - lie on the same side of the transversal and on the same side of 2 lines. 

Alternate exterior angles - nonadjacent exterior angles that lie on opposite sides of a transversal. 

Alternate interior angles - nonadjacent interior angles that lie on opposite sides of transversal 

Consecutive Interior Angles - interior angle that lie on same side of transversal

3.2 Angles and Parallel Lines 

Corresponding Angle Postulate - if 2 lines cut by a transversal are parallel, the corresponding angles are congruent. 

Alternate Interior Angles Theorem - If 2 lines cut by a transversal are parallel, the alternate interior angles are congruent. 

Consecutive Interior Angle Theorem - If 2 lines cut by a transversal are parallel, the consecutive interior angles are supplementary. 

Alternate Exterior Angles Theorem - If 2 lines cut by a transversal are parallel, the alternate exterior angles are congruent. 

Perpendicular Transversal Theorem - If 2 lines cut by a transversal are parallel and the transversal is perpendicular to one of the parallel lines, then it must also be perpendicular to the other line.

3.5 Proving Lines Parallel 

Converse of Corresponding Angle Postulate - If 2 lines are cut by a transversal so that corresponding angles are congruent, then the lines are parallel. 

Consecutive Interior Angle Theorem Converse - If 2 lines are cut by a transversal so that a pair of consecutive interior angles are supplementary, then the lines are parallel. 

Alternate Interior Angle Theorem Converse - If 2 lines are cut by a transversal so tha a pair of alternative interior angles are congruent, then the lines are parallel .

Alternate Exterior Angles Theorem Converse - If 2 lines are cut by a transversal so that a pair of alternate exterior angles are congruent, then the lines are parallel. 

Perpendicular Theorem Converse - If 2 lines are perpendicular to the same transversal, then the lines are parallel.