When two straight lines cross, they form four angles. The angles directly across from each other are called vertical angles.
Vertical angles are always equal. This isn't a coincidence — it's a mathematical certainty. If one is 70°, the one directly opposite is also 70°.
Remember
Vertical angles are the ones across the "X" from each other — not the ones next to each other. The ones next to each other are supplementary.
Real World
Look at a road intersection from above — two streets crossing form an X. The matching angles at opposite corners of that X are vertical angles.
Feeling ready?
Put this concept to work with a practice workout.