If an+1=121+an, then cos1-a02a1a2…….∞=

Given an+1=1+an2 Let a0=cosθ⇒a1=1+cosθ2=cosθ2    a2=cosθ4    a3=cosθ8  an+1=cosθ2n+1    and so onWe know that cosθ2cosθ22cosθ23..............cosθ2n−1............∞=sinθθ∴cos1-a02a1a2…….∞=cossinθsinθ·θ                                    =cosθ=a0