What are vertical angles?

Vertical angles are formed when two lines intersect, creating two pairs of opposite angles. Each angle in a pair is called a vertical angle to its counterpart, and they are always equal to each other. This means that if one angle measures, for example, 30 degrees, the vertical angle opposite it will also measure 30 degrees. This property arises from the fact that when two lines intersect, the angles adjacent to each other (the non-opposite angles) are supplementary, summing together to form 180 degrees.

Understanding vertical angles is fundamental in geometry, as they illustrate key concepts about angle relationships and the nature of intersecting lines. This definition clarifies that vertical angles are specifically those that sit across from each other, and is an essential concept in solving various problems concerning angles.