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'x(x,y)=x^4 u'‘xx(x,y)=4x^3 u''xx(1,2)=4 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(...
连续偏导数是什么意思?答:u'x(x,y)=x^4 u'‘xx(x,y)=4x^3 u''xx(1,2)=4 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(...