17 terms

parallel lines

perpendicular lines

lines that intersect at 90 angles

skew lines

lines that are not coplanar, not parallel and do not intersect

parallel planes

transversal lines

a line that intersects two or more lines

corresponding angles

alternate interior

alternate exterior

same side interior

corresponding angles postulate

if 2 parallel lines are cut by a transversal, then the pairs of corresponding angles are congruent

alt. int. angles thm.

if 2 parallel lines are cut by a transversal, then the pairs of alternate interior angles are congruent

alt. ext. angles thm

if 2 parallel lines are cut by a transversal, then the pairs of alternate exterior are congruent

same-side interior angles thm

If 2 parallel lines are cut by a transversal, then the same side interior angles are supplementary.

converse of the alt. int. angles thm

if 2 complanar lines are cut by a transversal so that a pair of alternate interior angles are congruent then the two lines are parallel

converse of the alt. ext. angles thm

if two coplanar lines are cut by a transversal so that a pair of alt ext angles are congruent then the two lines are parallel

Converse of the Same-Side Interior Angles Theorem

If two coplanar lines are cut by a transversal so that a pair of alternate interior angles are supplementary, then the two lines are parallel.

perpindicular bisector

A line that is perpendicular to a segment at its midpoint.