Vertical angles are angles located across from each other that are formed by two intersecting lines. Vertical angles are always congruent, meaning they have the same measure. Some examples show using vertical angles to determine the measure of unknown angles by setting up equations from the known congruency of vertical angles and solving.

1. Module 5 Lesson 3

2. When 2 lines cross, vertical angles are the angles across from each other.
Vertical angles are congruent.
What are vertical angles?
The angles represented by A
are vertical
The angles represented by B
are vertical

3. Try this easy one…
What is the measure of
AngleA?

4. 78!
Since vertical angles are congruent, angle A
is 78.
The answer is…

5. Maybe a little harder…
Solve for x.

6. X=86!
Since vertical angles are
congruent, you know x+9=95.
Solve for x by subtracting 9.
And the answer is…

7. Ok, try this one…
A=5x-17 and
C=2x+19. Find the
measure of angle
A.

8. 43 degrees!
Since the angles are vertical, you set
them equal to each other. 5x-17=2x+19
Solve for x and get 12.
Plug it in (it asks for the angle not x) to
get 43.
Answer…