You should learn the graphs of the trigonometric functions. These will help you remember the values of the trigonometric functions. For example, it is clear from the graph that sin(π)=0.
y=sin(x) (which looks like the letter S for sin)
y=cos(x) (which looks like the letter C for cos)
y=tan(x) (note that the vertical lines at x=π/2 and x=3π/2 are asymptotes and that the gradient of the graph at the origin and at x=pi is not zero: it is equal to 1)
You should learn the values of major angles in radians and the values of sin(x), cos(x) and tan(x) for these angles.
(Note that xc denotes an angle in radians. Where the angle is a multiple of π, the little c symbol is usually left out.)
You should make sure you know all of these identities. Clicking on a formula will take you to the page that explains what it is for. Hovering over the formula will give you its name.