设函数z=f(sinx,xy),其中具有二阶连续偏导数,求ε^2z/εxεy
<p>问题：设函数z=f(sinx,xy),其中具有二阶连续偏导数,求ε^2z/εxεy<p>答案：↓↓↓<p class="nav-title mt10" style="border-top:1px solid #ccc;padding-top: 10px;">李忠华的回答：<div class="content-b">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
页:
[1]