Question

find the value of cos3theta/2costheta-1​

Answer 1

The value of (cos3theta)/(2cos2theta-1) is equal to costheta.

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Answer 2

Answer:

Solution :

cos3θ+2cosθ=0

⇒4cos3θ−3cosθ+2cosθ=0

⇒4cos3θ−cosθ=0

⇒cosθ(4cosθ2−1)=0

⇒cosθ=0 or 4cos2θ−1=0

Now cosθ=0

⇒θ=(2n+1)π2.

and 4cos2θ−1=0

⇒cos2θ=14=(12)2=cos2π3

⇒θ=nπ±π3