In mathematics, vertical angles are always congruent. Vertical angles are the angles positioned opposite from each other when two lines intersect. They are called vertical because the angles share the same vertex, or corner point, not because they run vertically on a page.
To be congruent means to be precisely the same in shape and size. The term originates from the Latin word "congruere," which means "to agree." Angles that are congruent have the exact same degree measurement, as is the case with vertical angles. To be considered congruent, angles do not need to point in the same direction or be on lines that are the same size; they only need to have the same degree measurement.