Question

The value of cos 15° is ______.

विकल्प

• `(sqrt(3) + 1)/(2sqrt(2))`

• `(sqrt(2) + 1)/(3sqrt(3))`

• `(sqrt(2) - 1)/(3sqrt(3))`

• `(sqrt(3) - 1)/(2sqrt(2))`

Answer 1

The value of cos 15° is `underlinebb((sqrt(3) + 1)/(2sqrt(2))`.

Explanation:

cos 15° = cos(45° – 30°)

= cos 45° cos 30° + sin 45° sin 30°

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

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

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