sin² 6x – sin² 4x = sin2x sin10x

L.H.S = sin² 6x – sin² 4x
[Using the formulae 2sin²x = 1 - cos2x]
        =
        = - (cos12x – cos8x)
        = - [cos(10x + 2x) – cos(10x - 2x)]
[Using the formulae -2sinθ sinφ = cos(θ + φ ) - cos(θ - φ )]
        = × 2 sin10x sin2x
        = sin10x sin2x