Vertical angles are defined as which of the following?

Vertical angles are defined as which of the following?

• A. A pair of opposite congruent angles formed by intersecting lines
• B. A pair of adjacent angles formed by intersecting lines
• C. Angles formed by a line crossing a circle
• D. Angles that sum to 180 degrees

Answer: (A)

Vertical angles occur when two lines intersect, producing four angles at the point of intersection. The angles opposite each other across the intersection are vertical angles, and they have the same measure. So the best description is a pair of opposite angles formed by intersecting lines that are congruent. The other ideas describe different concepts: adjacent angles share a side and add to 180 degrees (a linear pair), and angles formed by a line crossing a circle refer to other geometric ideas.

Vertical angles occur when two lines intersect, producing four angles at the point of intersection. The angles opposite each other across the intersection are vertical angles, and they have the same measure. So the best description is a pair of opposite angles formed by intersecting lines that are congruent.

The other ideas describe different concepts: adjacent angles share a side and add to 180 degrees (a linear pair), and angles formed by a line crossing a circle refer to other geometric ideas.