Theorem angles are congruent. Transversal Alternate exterior angles Parallel lines Same-side Transversal same-side interior …the Interior Angles angles are supplementary. Same-side interior angles Theorem Supplementary Proving lines are parallel If 2 coplanar lines are cut by a transversal so that a pair of Transversal Corresponding corresponding angles are Angles congruent, THEN THE LINES Corresponding angles CONVERSE ARE PARALLEL. parallel If 2 coplanar lines are cut by Transversal a transversal so that a pair of Alternate alternate interior angles are Alternate interior angles Interior Angles congruent, THEN THE LINES CONVERSE parallel ARE PARALLEL. If 2 coplanar lines are cut by Transversal Alternate a transversal so that a pair of Exterior alternate exterior angles are Alternate exterior angles Angles congruent, THEN THE LINES parallel CONVERSE ARE PARALLEL. If 2 coplanar lines are cut by Transversal a transversal so that a pair of Same-side Same-side interior same-side interior angles are Interior Angles angles supplementary, THEN THE Supplementary CONVERSE LINES ARE PARALLEL. parallel Theorems about perpendicular lines If intersecting lines form a Linear pair 3-4-1 congruent linear pair, then perpendicular the lines are perpendicular.
Theorem angles are congruent. Transversal Alternate exterior angles Same-side Interior Angles Theorem …the same-side interior angles are supplementary. Parallel lines Transversal Same-side interior angles Supplementary Proving lines are parallel Corresponding Angles CONVERSE If 2 coplanar lines are cut by a transversal so that a pair of corresponding angles are congruent, THEN THE LINES ARE PARALLEL. Transversal Corresponding angles parallel Alternate Interior Angles CONVERSE If 2 coplanar lines are cut by a transversal so that a pair of alternate interior angles are congruent, THEN THE LINES ARE PARALLEL. Transversal Alternate interior angles parallel Alternate Exterior Angles CONVERSE If 2 coplanar lines are cut by a transversal so that a pair of alternate exterior angles are congruent, THEN THE LINES ARE PARALLEL. Transversal Alternate exterior angles parallel Same-side Interior Angles CONVERSE If 2 coplanar lines are cut by a transversal so that a pair of same-side interior angles are supplementary, THEN THE LINES ARE PARALLEL. Transversal Same-side interior angles Supplementary parallel Theorems about perpendicular lines 3-4-1 If intersecting lines form a congruent linear pair, then the lines are perpendicular. Linear pair perpendicular