How do you find trig functions without a calculator?

Question

For example: sin 300, cot 315, cos 180.

Answer 1

sin(300) = sin (360 - 60) = - sin(60) = -sqrt(3)/2

sin(315) = sin (360 - 45) = sin(-45) = -sin(45) = -sqrt(2)/2

cos(315) = cos(360 - 45) = cos 45 = sqrt(2)/2

cot(315) = cos(315)/sin(315) = [sqrt(2)/2]/[-sqrt(2)/2] = -1

cos(180) = cos(0 + 180) = - cos(0) = -1

Answer 2

I fail in trigo,good luck.