如图所示
解，cosa^2=cosa^2/(sina^2+cosa^2) =1/(tana^+1)=16/252sin2a=4sinacos/(sina^2+cosa^2) =4tana/(1+tana^2) =48/25则原式=64/25选(A)
求这道题的详解答过程谢谢。(´△｀)具体解答如图所示
