### Transversals

A **transversal** is a line that crosses two other lines. In both diagrams, the line *PQ* is a transversal to both the lines *AB* and *CD.*

### Corresponding angles

In each of the diagrams below, the two marked angles are called **corresponding angles** because they are in corresponding positions around the two vertices *M* and *N*.

### Corresponding angles and parallel lines

If the lines *AB* and *CD* are parallel, then the corresponding angles \(\angle\)*DGF* and \(\angle\)*BHF*, marked \(\alpha\) and β, are equal.

#### Example 1

Find θ in the diagram.

#### Solution

θ = 121° (corresponding angles *AB || CD*)