cos 60° cos 30° − sin 60° sin 30°

On substituting the values of various T-ratios, we get:

 cos 60o cos 30o − sin 60o sin 30o 

$=\left(\frac{1}{2} \times \frac{\sqrt{3}}{2}-\frac{\sqrt{3}}{2} \times \frac{1}{2}\right)=\left(\frac{\sqrt{3}}{4}-\frac{\sqrt{3}}{4}\right)=0$