令A=x^2+y^2+z^2∂(lnr)/∂x=∂(lnA)/2∂x=x/A∂^2(lnr)/∂x^2=(A-2x^2)/A^2=(y^2+z^2-2x^2)/A^2类似的∂^2(lnr)/∂y^2=(x^2+z^2-2y^2)/A^2∂^2(lnr)/∂z^2=(x^2+y^2-2z^2)/A^2
