Chapter 13

Lines & Angles

A straight line is 180°. Think of a line as half of a circle:

Parallel lines are lines that lie in a plane and never intersect. No matter how far you extend the lines, they never meet. Two parallel lines are shown below:

Perpendicular lines are lines that intersect at a 90° angle. Two perpendicular lines are shown here:

There are two major line-angle relationships that you must know for the GRE:

1. The angles formed by any intersecting lines.
2. The angles formed by parallel lines cut by a transversal.