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Vertical Angles Congruence Theorem
See It in Action
Two examples of the idea done right—and one common look-alike that is not right.
EXAMPLE
EXAMPLE
NON-EXAMPLE
Definition
The Vertical Angles Congruence Theorem states that:
“If two angles are vertical angles, then they are congruent.”
In simple terms:
When two lines intersect, they form two pairs of opposite (vertical) angles. This theorem tells us that each pair of vertical angles will always be equal in measure.
In symbols:
If ∠1 and ∠2 are vertical angles,
then ∠1 ≅ ∠2
Example:
If two lines cross and create angles labeled ∠A and ∠B opposite each other, then
∠A ≅ ∠B
This theorem is often used in geometry proofs involving intersecting lines.
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