Question

write principal value of: (cos-1root3/2 +cos-1(-1/2))

Answer 1

$cos^{-1}\frac{\sqrt3}{2}+cos^{-1}(-\frac{1}{2})\\\\Cos^{-1}\ \ has\ principal\ values\ in\ 0\ to\ +\pi\\\\ =\frac{\pi}{6} + \frac{2}{3}\pi\\\\=\frac{5}{6}\pi=150 deg.$