Vertical angles
Vertical angles are the angles opposite each other when two lines cross. They are always equal. In this diagram, angles A and C are vertical (and equal) as well as angles D and B:
Now here's a problem for you:
In this diagram, which angles are equal, assuming that the 2 horizontal lines are parallel?
____ , ____ , ____ , and ____ are equal, as well as
____ , ____ , ____ , and ____.


