Exterior angles formed by Non-Parallel lines and their Transversal

The external angles, formed by the intersection of two nonparallel lines and their transversal are called the exterior angles of nonparallel lines and their transversal.

Exterior angles

Geometrically, four exterior angles are possibly formed when two non-parallel lines are intersected by their transversal.

$1. \,\,\,\,\,\,$ $\angle BPX$ is first exterior angle

$2. \,\,\,\,\,\,$ $\angle XPA$ is second exterior angle

$3. \,\,\,\,\,\,$ $\angle CQY$ is third exterior angle

$4. \,\,\,\,\,\,$ $\angle YQD$ is fourth exterior angle

The above four angles are formed externally when two nonparallel lines are cut by a straight line. Hence, they are called as exterior angles.