trigonometry - Sum of sinx+sin3x+sin5x+......sin(2n-1)x

Options are

1. n/2 cosx- 1sin(nx)/2sinx . cos(n+2)x


2. n/2.sinx-1/2sin(nx)


3. n/2.cosx - cos(n+2)x


4. sinx +sin(nx)