geometry

alternate exterior angles

If a transversal intersects two parallel lines, then alternate exterior angles are congruent.

same side exterior angles

If a transversal intersects two parallel lines, then same-side exterior angles are supplementary.

Congruent Complements Theorem

If two angles are complementary to the same angle (or to congruent angles), then they are congruent.

Right Angle Supplements Theorem

If two angles are congruent and supplementary, then each is a right angle.

Congruent Supplements Theorem

If two angles are supplementary to the same angle (or to congruent angles), then they are congruent

Vertical Angles Theorem

If two angles are vertical angles, then they are congruent.

Converse of the Same-Side Interior Angles Theorem

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

converse of alternate exterior angles theorem

If two lines and a transversal form alternate exterior angles that are congruent, then the two lines are parallel.

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.

Converse of the Corresponding Angles Postulate

If two lines and a transversal form corresponding angles that are congruent, then the two lines are parallel.

alternate interior angles

If two parallel lines are cut by a transversal, then the alternate interior angles are congruent.

Corresponding Angles Postulate

If two parallel lines are cut by a transversal, then the pairs of corresponding angles are congruent

same side interior angles

If two parallel lines are cut by a transversal, then the two pairs of same-side interior angles are supplementary. (m<1 + m<2 = 180)

Right Angle Theorem

All right angles are congruent

converse of same exterior angles theorem

if 2 lines and a transversal form same-side ext angles that are supplementary then 2 lines are parallel