Trigonometry
Without using a calculator, determine the exact value of the expression.
cos(cos−1(−12))\cos\left(\cos^{-1}\left(-\frac12\right)\right)cos(cos−1(−21))
32\frac{\sqrt3}{2}23
−22-\frac{\sqrt2}{2}−22
−12-\frac12−21
22\frac{\sqrt2}{2}22