What are vertical angles formed by?

Vertical angles are formed by two intersecting lines. When two lines cross each other, they create pairs of opposite angles. Each pair of opposite angles is referred to as vertical angles. These angles are congruent, meaning they have the same measure. For example, if two lines intersect and one angle measures 50 degrees, the angle directly opposite it on the other side of the intersection will also measure 50 degrees. This relationship is a fundamental property of intersecting lines and is crucial for solving various geometric problems.

The other options relate to different geometric properties but do not define vertical angles. Two parallel lines do not intersect and thus cannot create any angles at all. Perpendicular lines intersect at right angles, forming various types of angles, but the angles opposite to each other at the point of intersection are still designated vertical angles. Adjacent angles share a common side and vertex but are not opposite to each other and do not meet the criteria for vertical angles.