Write the correct alternative in the following:

If f(x) = (cos x + i sinx) (cos 2x + i sin 2x) (cos 3x + i sin 3x) …. (cos nx + i sin nx) and f(1) = 1, then f’’ (1) is equal to


Given:


f(x) = (cos x + i sinx) (cos 2x + i sin 2x) (cos 3x + i sin 3x) …. (cos nx + i sin nx)


Since


So,









1