cot4x(sin5x + sin3x) = cotx(sin5x – sin3x)

L.H.S = cot4x(sin5x + sin3x)
[Using the formula sin5x + sin3x = 2 sin cos ]
        = 2cot4x sin cos
        = 2cot4x sin cos
        = 2cot4x sin4x cosx
        = 2cos4x cosx
R.H.S = cotx(sin5x – sin3x)
[Using the formula sin5x - sin3x = 2 cos sin ]
        = 2cotx cos sin
        = 2cotx cos sin
        = 2cos4x cosx
∴ L.H.S = R.H.S