[" 85.",sin7x=sin3x],[" 86.",cos3x-sin2x=0]

cos3x tan5x=sin7x

Prove that: ("sin"3x+"sin"x)"sin"x+(cos3x-cosx)cosx=0

3-2cos x-4sin x-cos2x+sin2x=0

Prove that: (i) sin 3x+"sin" 2x-"sin" x = 4 sin x cos((x)/(2))cos((3x)/(2)) (ii) ("sin" 3x+"sin" x)"sin" x+(cos 3x-cos x)cos x=0.

lim_(x rarr0)(sin3x cos2x)/(sin2x)

Prove that: ,,(sin x+sin3x)/(cos x+cos3x)=tan2x

Prove that: (sin3x+sin x)sin x+(cos3x-cos x)cos x=0

(sin3x + sin x) sin x + (cos3x-cos x) cos x = 0