tanαtanβ+1=（tanα-tanβ）/tan（α-β）tanθtan2θ+1=(tan2θ-tanθ)/tan(2θ-θ)=(tan2θ-tanθ)/tanθtan2θtan3θ+1=(tan3θ-tan2θ)/tan(3θ-2θ)=(tan3θ-tan2θ)/tanθ.tan(nθ)tan(n+1)θ+1=[tan(n+1)θ...