The relationships between the six major trigonometric functions (sine, cosine, tangent, secant, cosecant, and cotangent) can all be seen on a single right-angled triangle inside a circle. As you drag the red point around the edge of the circle, you can see how the six functions increase or decrease in value. Only sine and cosine stay inside the circle; at some angles, the others escape to infinity.

Mouseover the function name to see its current value. [less]