Question

Find the value of $x$ if $\cos x=\cos {60}^o\cos {30}^o+\sin {60}^o\sin {30}^o$

Answer 1

$\cos x=\cos {60}^{\circ }\cos {30}^{\circ }+\sin {60}^{\circ }\sin {30}^{\circ }\cos x=\cos {(60}^{\circ }-{30}^{\circ })\cos x=\cos {30}^{\circ }x={30}^{\circ }$