Geometry Angle Pairs: Parallel Lines and Transversals

Alternate Interior Angles

Inside the two lines, on opposite sides of the transversal. If lines are parallel, they are CONGRUENT.

Alternate Exterior Angles

Outside the two lines, on opposite sides of the transversal. If parallel, they are CONGRUENT.

Corresponding Angles

Same relative position at each intersection (F pattern). If parallel, they are CONGRUENT.

Same-Side Interior Angles

Inside the two lines, same side of transversal. Also called Consecutive Interior. If parallel, they are SUPPLEMENTARY (180°).

Same-Side Exterior Angles

Outside the two lines, same side of transversal. Also called Consecutive Exterior. If parallel, they are SUPPLEMENTARY.

Vertical Angles

Opposite angles at same intersection. Always CONGRUENT.

Linear Pair

Two adjacent angles that make a straight line. Always SUPPLEMENTARY.

Supplementary

Two angles that add to 180°.

Complementary

Two angles that add to 90°.

Congruent

Same measure / equal. Marked with same number of arcs.

Transversal

A line that cuts through two or more other lines.

Parallel Lines

Two lines that never intersect. Marked with >> arrows. Makes special angle pairs congruent/supplementary.

Perpendicular Lines

Two lines that intersect at 90°.