Vertical Angles Theorem

Definition: Vertical Angles are angles whose sides form 2 pairs of opposite rays. When 2 lines intersect, 2 pairs of vertical angles are formed. One pair of vertical angles is shown below. (Click the other checkbox on the right to display the other pair of vertical angles.) Interact with the following applet for a few minutes, then answer the questions that follow.
Directions & Questions: 1) Complete the following statement (based upon your observations). Vertical angles are always __________________________. 2) Suppose the pink angle above measures 140 degrees. What would the measure of its vertical angle? What would be the measure of the other 2 (gray) angles?