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. This applet displays the special angles and their sine and cosine. It can be used to investigate coterminal angles, reference angles, identities such as sin(π  A) =  sin(A) and many other topics in trigonometry.
Interactive Tutorial
Investigate angle interactively using An html5 applet on Angles in Standard Position.
 click on the button above "start/restart" 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?
 What is the relationship between the trigonometric ratios of related angles?
Investigating identities
 Example 1: type 30° in angle A and 150° in angle B and click start. What symmetry is there between the two angles? What is the relationship between the sine and cosine of these two angles?.
 Example 2: type 120° in angle A and 30° in angle B and click start. What symmetry is there between the two angles? What is the relationship between the sine and cosine of these two angles?.
 Example 3: type 60° in angle A and 60° in angle B and click start. What symmetry is there between the two angles? What is the relationship between the sine and cosine of these two angles?.
More references on angles.

