Question

求下列函数的全微分u=ln(x^2+y^2+z^2)

Answer 1

u'x=2x/(x^2+y^2+z^2)

u'y=2y/(x^2+y^2+z^2)

u'z=2z/(x^2+y^2+z^2)

du=2xdx/(x^2+y^2+z^2) +2ydy/(x^2+y^2+z^2) +2zdz/(x^2+y^2+z^2)

多元函数微分问题，上面三个是偏微分，总的就加起来