Math Homework. Do It Faster, Learn It Better.
Vertical Angles Theorem
Theorem:Vertical angles are always congruent.
In the figure, and .
Proof:
form a linear pair, so by the Supplement Postulate, they are supplementary. That is,
.
form a linear pair also, so
.
Subtracting from both sides of both equations, we get
.
Therefore,
.
You can use a similar argument to prove that .