Question

Find the value of x :

$\cos x=\cos {60}^o\cos {30}^o+\sin {60}^o\sin {30}^o$

Answer 1

$\cos x=\cos {60}^o\cos {30}^o+\sin {60}^o\sin {30}^o$

$\cos x=\frac{1}{2}\times \frac{\sqrt{3}}{2}+\frac{\sqrt{3}}{2}\times \frac{1}{2}$

$\cos x=\frac{\sqrt{3}}{2}$

$\cos x=\cos {30}^o$

$x={30}^o$