设An=tanBn,Bn=arctanAn.B1=arctanA1=arctan1=π/4,A(n+1)=An +2/An tanB(n+1)=tanBn+2/tanBnsinB(n+1)/cosB(n+1）=sinBn/cosBn+2cosBn/sinBn=[1+(cosBn)^2]/(sinBncosBn)=[1+(1+cos2Bn)/2]/(sinBncosBn)=(3+cos2Bn)...