Simple Trigonometry

Remember the above image and we can derive the below values easily

sin(0) = cos(90) = sin(180) = cos(270) =  sin(360) = cos(-90) = 0
cos(0) = sin(90) = 1
cos(180) = sin(270) = -1

sin(A + B) = sin A cos B + cos A sin B
cos(A + B) = cos A cos B − sin A sin B

sin(A − B) = sin A cos B − cos A sin B
cos(A − B) = cos A cos B + sin A sin B