Prove that tan 4θ=4tan θ(1−tan2θ)1−6 tan2θ+tan4θ
Prove that tan tan 4 θ=4 tan θ (1−tan2θ)1−6 tan2 θ+tan4 θ. Find the angle θϵ(0,π2), in which the given proof does not hold.
Or
Prove that cos4x+cos3x+cos2xsin4x+sin3x+sin2x = cot 3x . Do you think at x=π3, the given proof holds true?