Question

(4cos 40 degree - cos 20 degree)^4 /(sin 20 degree)^4

Answer 1

Answer:

Hope it helps you.

Step-by-step explanation:

Let us consider the LHS 4(cos3 10° + sin3 20°) As we know that, sin 60° = √3/2 = cos 30° Sin 30° = cos 60° = 1/2 Therefore, Sin (3×20°) = cos (3×10°) 3sin 20° – 4sin320° = 4cos310° – 3cos 10° (As we know, sin 3θ = 3sin θ – 4sin3 θ and cos 3θ = 4cos3θ – 3cosθ) Therefore, 4(cos310° + sin320°) = 3(sin 20° + cos 10°) = RHS Thus proved.