The following applet illustrates what it means for two angles to be classified as congruent angles.
Interact with this applet for a few minutes, then answer the questions that follow.
Be sure to move the BIG PINK POINTS around each time before you re-slide the slider.

Questions:
1) What geometric transformation(s) took place in the applet above? List it/them.
2) Did any of these transformations change the measure of the original green angle?
3) Cause:
How would you define what it means for angles to be congruent with respect to the geometric
transformations you listed in (1) above?
4) Effect:
If we know that two angles are congruent, what can we consequently conclude about their measures?