What is the value of ∏k=1ncos(θ2k)\prod_{k=1}^{n} \cos\left(\frac{\theta}{2^k}\right)∏k=1ncos(2kθ)?
sinθ2nsin(θ/2n)\frac{\sin \theta}{2^n \sin(\theta/2^n)}2nsin(θ/2n)sinθ
sin2θ2nsin(θ/2n)\frac{\sin 2\theta}{2^n \sin(\theta/2^n)}2nsin(θ/2n)sin2θ
sinθ2ncos(θ/2n)\frac{\sin \theta}{2^n \cos(\theta/2^n)}2ncos(θ/2n)sinθ
cosθ2nsin(θ/2n)\frac{\cos \theta}{2^n \sin(\theta/2^n)}2nsin(θ/2n)cosθ