Opposite angles are across the transversal.
Opposite angles are equal.

Corresponding Angles

Corresponding angles are in the same position relative to lines intersected by a transversal.
Corresponding angles are equal when the two lines intersected by the transversal are parallel.

Alternate Angles

Alternate angles are in opposite positions relative to a transversal intersecting two lines.
Alternate angles are equal when the two lines intersected by the transversal are parallel.

Co-interior Angles

Co-interior angles are on the same side of an transversal line when it intersect two other lines.
Co-interior angles add to \(180^\circ\).

Supplementary Angles

Two angles are supplementary when they add up to 180 degrees (they make a straight line).

\(\angle A\) and \(\angle B\) below form a straight line so they must add to 180 degrees.

Complementary Angles

Two angles are complementary when they add up to 90 degrees (a right angle).

\(\angle{DAC}\) and \(\angle{CAB}\) form a right angle and would add up to 90 degrees.

Refer to the figure below. Guess which angles correspond with each type then press the button to show the answer.