• 试题 ID 23981


验证:$r=\sqrt{x^2+y^2+z^2}$ 满足 $\frac{\partial^2 r}{\partial x^2}+\frac{\partial^2 r}{\partial y^2}+\frac{\partial^2 r}{\partial z^2}=\frac{2}{r}$ .
A
B
C
D
E
F
答案:

答案与解析仅限VIP可见

解析:

答案与解析仅限VIP可见