Question

设z=㏑√(x²+y²)求（dz/dx）²+(dy/dx)²

Answer 1

z=0.5㏑(x²+y²)

dz/dx =x/(x²+y²)

dy/dx=y/(x²+y²)

所以（dz/dx）²+(dy/dx)²=1/(x²+y²)