The Total solution for NCERT class 6-12
Consider
LHS = cos 4x
We can write it as
= cos 2(2x)
Using the formula cos2A = 1 – 2 sin2 A
= 1 – 2 sin2 2x
Again by using theformula sin2A = 2sin A cos A
= 1 – 2(2 sin x cos x) 2
So we get
= 1 – 8 sin2x cos2x
= R.H.S.