Question

3.
which of the following is rational number
1) sin 15
2) cos 15
3) sin 15° cos 15 4) sin 15° cos 750​

Answer 1

Option (C).

Sin 15 cos 15 can be written as

= 1/2 2 sin 15 cos 15  (2 sin a cos a = sin 2a)

= 1/2 sin (2 * 15)

= 1/2 sin 30

= 1/2 * 1/2

= 1/4.