| A | B |
|---|
| Postulate 3-1 Corresponding Angles Postulate | If a transversal intersects two parallel lines, then corresponding angles are congruent. |
| Theorem 3-2 Alternate Interior Angles Theorem | If a transversal intersects two parallel lines, then alternate interior angles are congruent. |
| Theorem 3-2 Same-Side Interior Angles Theorem | If a transversal intersects two parallel lines, then same-side interior angles are supplementary. |
| Postulate 3-2 Converse of the Corresponding Angles Postulate | If two lines and a transversal form corresponding angles that are congruent, then the two lines are parallel. |
| Theorem 3-3 Converse of the Alternate Interior Angles Theorem | If two lines and a transversal form alternate interior angles that are congruent, then the two lines are parallel. |
| Theorem 3-4 Converse of the Same-Side Interior Angles Theorem | If two lines and a transversal form same-side interior angles that are supplementary, then the two lines are parallel. |
| Theorem 3-5 Multiple parallel lines | If two lines are parallel to the same line, then they are parallel to each other. |
| Theorem 3-6 Parallel and perpendicular lines | In a plane, if two lines are perpendicular to the same line, then they are parallel to each other. |
| Theorem 3-7 Triangle Angle-Sum Theorem | The sum of the measures of the angles of a triangle is 180. |
| Theorem 3-8 Triangle Exterior Angle Theorem | The measure of each exterior angle of a triangle equals the sum of the measures of its two remote interior angles. |
| Triangle Exterior Angle Theorem Corollary | The measure of an exterior angle of a triangle is greater than the measure of either of its remote interior angles. |
| Parallel Postulate | Through a point not on a line, there is one and only one line parallel to a given line. |
| Spherical Geometry Parallel Postulate | Through a point not on a line, there is no line parallel to a given line. |
| Theorem 3-9 Polygon Angle-Sum Theorem | The sum of the measures of the angles of an n-gon is |
| Theorem 3-10 Polygon Exterior Angle-Sum Theorem | The sum of the measures of the exterior angles of a polygon, one at each vertex, is 360. |
| Slopes of Parallel Lines | If two nonvertical lines are parallel, their slopes are equal. If the slopes of two distinct nonvertical lines are equal, the lines are parallel. Any two vertical lines are parallel. |
| Slopes of Perpendicular Lines | If two nonvertical lines are perpendicular, the product of their slopes is -1. If the slopes of two lines have a product of -1, the lines are perpendicular. Any horizontal line and vertical line are perpendicular. |
