Angle Relationships

Vertical angles are the angles opposite each other when two lines intersect. They are always equal in measure.

Complementary angles are two angles whose measures add up to 90 degrees.

Supplementary angles are two angles whose measures add up to 180 degrees.

To find the measure of an angle when given its complement, subtract the measure of the known angle from 90 degrees.

To find the measure of an angle when given its supplement, subtract the measure of the known angle from 180 degrees.

Adjacent angles are two angles that share a common side and a common vertex but do not overlap.

A linear pair of angles consists of two adjacent angles whose non-common sides form a straight line. They are supplementary.

The sum of the angles in a triangle is always 180 degrees.

Corresponding angles are angles that are in the same position on two parallel lines cut by a transversal. They are equal in measure.

Alternate interior angles are angles that lie between two parallel lines on opposite sides of a transversal. They are equal in measure.