(3(cos20)^2-(sin20)^2)/(sin20cos20)^2+64(sin20)^2=16((sin60cos20+cos60sin20)(sin60cos20-cos60sin20))/(sin40)^2+64(sin20)^2=16(sin80sin40)/(sin40)^2+64(sin20)^2=32cos40+64(sin20)^2=32*(1-2(sin20)^2)+64(sin20)^2=32
楼上的写出解答过程我就不多说了
一楼的正解