Cevap:
Let cos-1x be θ ⇒ x = cos θ In RHS, putting the value of x cos-1 (4x3 – 3x) ⇒ cos-1(4cos3θ – 3cosθ) ⇒ cos-1 (cos 3θ) [∵ 4cos3θ – 3cosθ = cos 3θ] = 30 putting the value of 0 = 30 ⇒ 3 cos-1 x = LHS LHS = RHS provedRead more on Sarthaks.com - https://www.sarthaks.com/608029/prove-that-3cos-1x-cos-1-4x-3-3x-x-1?show=608034#a608034
