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Vertical Angles

If two lines intersect, then the two angles on opposite sides of the vertex are called vertical angles.

Supplementary Angles

Two angles are called supplementary if they add up to 180 degrees.

Transversal Line

A transversal is a line that crosses a pair of given lines.

Same-side Interior Angles

A pair of angles like 4 and 6.

Alternate Interior Angles

A pair of angles like 3 and 6.

Same-side Exterior Angles

A pair of angles like 2 and 8.

Alternate Exterior Angles

A pair of angles like 2 and 7.

Corresponding Angles

A pair of angles like 1 and 5.

An Angle

An angle is a measure of an amount of turning. It is often represented by two rays meeting at a common vertex.