Angle Pairs Formed by a Transversal

8 angles are formed when a transversal crosses two parallel lines and they have the following relationships.

the angles which occupy the same relative position at each intersection where a straight line crosses two others. Angles are equal.

Corresponding angles

the angles that lie on the inner side of the parallel lines but on the opposite sides of the transversal. Angles are equal.

Alternate Interior angles

the angles that lie on the outer side of the parallel lines but on the opposite sides of the transversal. Angles are equal.

Alternate Exterior angles

two angles that are on the same side of the transversal and on the interior. Angles are supplementary.

Same-side Interior/Consecutive Angles

There are only two relations; equal or supplementary. Angles are equal if they are the same angle type, angles are supplementary if they are opposite angle types.