
Line Intersection Theorem:
two different lines intersect in at most one point.

Betweenness Theorem:
If B is between A nad C, then AB + BC = AC

Theorem (unnamed):
For any three points A, B, and C, AB + BC > AC.

Linear Pair Theorem:
Vertical Angle Theorem:
 If two angles form a linar pair, then they are supplementary.
 If two angles are vertical angles, then they have equal measures.

Perpendicular Lines and Slopes Theorem:
Two nonvertical lines are perpendicular if and only if the product of their slopes = 1.

Parallel Lines and Slopes Theorem:
Two nonvertical lines are parallel if and only if they have the same slope.

