���˿���

Intersecting lines are lines that cross each other. The point where they meet is called a vertex.

When two lines intersect, the opposite (X) angles are equal.

In the diagram above, the two green angles are equal and the two yellow angles are equal.

These X angles are called vertically opposite angles because they are opposite each other at a vertex.

If you know one angle in a pair of vertically opposite angles, the other will be the same.