Vertical Angles

When two lines are intersect they made four angles, angles are opposite to one another at the intersection of two lines.

Each opposite pair of angles are called “Vertical Angles”, and vertical angles are always “Congruent”

They are also called  “Vertically Opposite Angles”.                     

In above figure, ∠1 is vertically opposite to and ∠2, and ∠3 is vertically opposite to and ∠4.