This large window applet helps you understand the definition and properties of an angle in standard position. It can also be used to understand the concept of coterminal angles.
Interactive Tutorial
Two ways to investigate angle interactively.
1) An html5 applet on Angles in Standard Position.
2) and a java applet below
 click on the button above "click here to start" and MAXIMIZE the window obtained.
 Type in any angle (in degrees, negative or positive) then click on start.

coterminal angles : Type in the following angles: 390 degrees, 30 degrees, 330 degrees. Each time note the position of the terminal side. Do these angles have the same terminal side? Why?
More references on angles.
