Geometry Unit 3 Postulates and Theorems
Same-Side Interior Angles Postulate
If a transversal intersects two parallel lines, then same-side interior angles are supplementary.
Alternate Exterior Angles Theorem
If a transversal intersects two parallel lines, then alternate exterior angles are congruent.
Alternate Interior Angles Theorem
If a transversal intersects two parallel lines, then alternate interior angles are congruent.
Corresponding Angles Theorem
If a transversal intersects two parallel lines, then corresponding angles are congruent
Converse of the 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 Theorem
If two lines and a transversal form corresponding angles that are congruent, then the lines are parallel.
Converse of the Same-Side Interior Angles Postulate
If two lines and a transversal form sameside interior angles that are supplementary, then the two lines are parallel.
Perpendicular Transversal Theorem
In a plane, if a transversal is perpendicular to one of two parallel lines, then it is perpendicular to the other line.
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.
In a plane, if two lines are perpendicular to the same line,
then they are parallel to each other.
Triangle Angle-Sum Theorem
The sum of the measures of the angles of a triangle is 180.