Geometry · Points, Lines & Angles
Vertical Angles
HSG-CO.A.1
Definition
The pair of opposite, congruent angles formed when two lines intersect.
Examples
- When two lines cross, the opposite angles are vertical angles and always equal, such as 50 = 50 degrees.
- Vertical angles are never adjacent — they sit directly across from each other.
Key rule
Vertical angles are always congruent.
Memory hook
Across the X, the angles match.