The screen is designed to help you to visualize the principal trigonometric functions sin, cos and tan. You can also see their inverse functions, their reciprocal functions and square functions. Relationships between these functions can be investigated. Identities such as cos²x + sin²x = 1 become clear.

To look at a function, check the relevant box on the right of the screen. You can choose which ones to draw and compare.
Play around. I hope you will find this applet helpful in understanding these important functions.