Classify the following pair of angles as complementary, supplementary, vertical, or neither.
Before you classify them, let’s do a quick rundown of what complementary, supplementary, and vertical angles are. Two angles are complementary if the sum of their measure is 90 degrees. Two angles are supplementary if the sum of their measure is 180 degrees. Vertical angles are angles opposite each other when two lines cross. And of none of the others are true, we can choose neither.
Which of these words apply to the picture on the left? We haven’t been given any information about the angle measure of angle one or two. But we can see that angle one and angle two are opposite each other. They’re directly across from one another. This means that they fit the definition of vertical angles. Angle one and angle two are vertical angles.