What is arcsin? arccos?

This animation, created using MATLAB, illustrates some key differences between the trig function (sine, cosine) and its inverse function. Trig functions take ANGLES as inputs and produce RATIOS as outputs. Vice versa for trig inverse functions. Also, the restricted domains (for sine and cosine) are VERY important when discussing inverse functions: if the domain for cosine was not restricted to [ 0,pi], then it would not be 1-to-1, implying no inverse function could exist. The last example here shows that sin(-5pi/6) = -1/2, however, arcsin(-1/2) = -pi/6..... (not -5pi/6). Be careful when "reversing" trig functions.