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问题：设函数z=f(sinx,xy),其中具有二阶连续偏导数,求ε^2z/εxεy
答案：↓↓↓ 李忠华的回答： 网友采纳 设u=sinx,v=xy dz/dx=dz/du*du/dx+dz/dv*dv/dx=cosxf1'+yf2' d^2z/dxdy=d(dz/dx)/dy=(-sinx)f1'+cosx*df1'/dx+y*df2'/dx =-sinxf1'+cosx(df1'/du*du/dx+df1'/dv*dv/dx)+y(df2'/du*du/dx+df2'/dv*dv/dx) =-sinxf1'+cosx(cosxf11''+yf12'')+y(cosxf21''+yf22'') =-sinxf1'+(cosx)^2f11''+(y+ycosx)f12''+y^2f22'' f1',f11'',f12'',f22''分别指df/du,d^2f/du^2,d^2f/dudv,d^2f/dv^2 | 
