Question

Evaluate:

cos 60° cos 30° − sin 60° sin 30°

Answer 1

We know that,

cos 60° = 1/2 = sin 30°

and cos 30° = √3/2 = sin 60°

Now,

cos 60° cos 30° — sin 60° sin 30° 

= (1/2) × (√3/2) – (√3/2) × (1/2)

= (√3/4) – (√3/4)

= 0