设函数u(x, y)具有二阶连续偏导数, L为自点(0,0)沿曲线y = sin x至...答:u'‘xy(x,y)=0 u''xy(1,2)=0u(x,2x)=x^2对x求导:u’x(x,2x)+2u'y(x,2x)=2x,再对x求导:u’‘xx(x,2x)+2u’‘xy(x,2x)+2u''yx(x,2x)+4u''yy(x,2x)=2u’‘xx(1,2)+2u’‘xy(1,2)+2u''yx(1,2)+4u''yy(1,2)=2u''yy(1,2)=-1/2偏导数是对二元...
设函数z=f(u,v)具有二阶连续偏导数,试求函数z=f(x,yx)对x的二阶偏导数...答:z=f(x,yx)dz/dx=f1'(x,yx)+f2'(x,yx)*y d^2z/dx^2=f11''(x,yx)+f12''(x,yx)*y+yf21''(x,yx)+yf22''(x,yx)*y =f11''(x,yx)+(y+1)*f12''(x,yx)+y^2*f22''(x,yx)