Angles, Lines & Triangles

Master angle rules, parallel lines, and triangle properties to solve any geometry question with confidence.

Angle Rules

Learn the core angle facts — angles on a line, around a point, vertically opposite — and use them to find missing angles.

Exterior Angles of Triangles

Learn the exterior angle theorem and use it to find missing angles in triangles quickly.

Angles in Parallel Lines

Identify alternate, corresponding, and co-interior angles formed by a transversal crossing parallel lines.