Properties of Parallel Lines

Corresponding Angles and Alternate Angles

When two lines and on a plane intersect a third line , eight angles are formed. Among these angles:
Angles in the same relative position are called corresponding angles.
On the other hand, angles that are positioned on opposite sides of the intersecting line are called alternate angles, such as:

Properties of Corresponding Angles and Alternate Angles in Parallel Lines

When two distinct lines intersect a third line:
  1. If the two lines are parallel, the corresponding angles are equal.
  2. If the two lines are parallel, the alternate angles are equal.
  3. If the corresponding angles are equal, the two lines are parallel.
  4. If the alternate angles are equal, the two lines are parallel.