Definition of Vertical Angles

Vertical Angles are formed when you have intersecting lines:

Source

Vertical angles, plain and simple, are the angles opposite of each other. The second thing that you have to know is that vertical angles are congruent, they have the same measure.

<1 and <8 form a vertical pair.

If <1=70, then <8=70 as well.

<2 and <5 form a vertical pair.

<3 and <4 form a vertical pair.

<6 and <7 form a vertical pair.

As usual, if you have any questions just comment!