Question

The value of cos 480° sin 150° + sin 600° cos 390° is ______.

Options

• 0

• 1

• `1/2`

• – 1

Answer 1

The value of cos 480° sin 150° + sin 600° cos 390° is – 1.

Explanation:

cos 480° sin 150° + sin 600° cos 390°

= [cos (540° – 60°) sin (180° – 30°) + sin (540° + 60°) cos (360° + 30°)]

= – cos 60° sin 30° + (– sin 60°) cos 30°

= `- 1/2 . 1/2 + (- sqrt(3)/2)(sqrt(3)/2)`

= `-1/4 - 3/4`

= – 1