cos (arctan (1))=
arctan (1) = 45 take it to the third quadrant = add 180 = 225
cos (225) = -1 / sqrt(2)
never leave a sqrt in the denominator
= -1 /sqrt(2) * sqrt(2)/sqrt(2)
= -sqrt(2)/2
sin (arccos (1/2)
arccos (1/2) = 60 take it to the 4th quadrant -60 degrees
sin (-60)
- sin 60
- sqrt(3)/2
