Question

Find the values of the following: $\cos \left({-600}^o\right)$

Answer 1

$=\cos (-{600}^o)=\cos {600}^o=\cos (720-{120}^o)$

$=\cos \left({120}^o\right)$

$=\cos (180-{60}^o)$

$=-\cos {60}^o$

$=\frac{-1}{2}$