360 degrees = 2p radians
so, 180 degrees = p radians
The original angle can be found by using the
inverse trig function. For example:
Sometimes in the literature, arcsin is written
as sin-1 and so on to indicate that it is an inverse function.
In the following examples, the side lengths are found using the
sin 45o = cos 45o = 1/1.4142 =
tan 45o = cot 45o = 1/1 = 1
sin 30o = cos 60o = 1/2 =
cos 30o = sin 60o = 1.7321/2 =
tan 30o = cot 60o = 1/1.7321 =
cot 30o = tan 60o = 1.7321/1 =
Then, there are the special cases of 0 and 90o.
The sin and cos for the full circle (0 to 360o) are
spelled out in the quadrant trigonometry facts