求由方程x-y+ 1/2 siny=0所确定的隐函数y的二阶导数d^2y/dx^2 ..将每一个偏导数分别求出来,再代入就可以了! == 也可以对f'(x)对x求导
y'=sec^2(x^2)*(x^2)'=2xsec^2(x^2)
y''=2sec^2(x^2)+4x*sec(x^2)*sec(x2^)tan(x^2)*(x^2)'
=2sec^2(x^2)+8x^2*sec^2(x^2)*tan(x^2)
y'=(secxtanx+sec^2x)/(secx+tanx)=secx
y''=secx*tanx