- #1

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∫d

**x**ρ(r,θ)δ(

**x**+

**u**(

**x**)-

**x')**

where ρ is a known mass density and

**u**=

**r**u_r+

**θ**u_θ a known vector function of spherical coordinates (r,θ) (no azimuthal dependence). How should the Dirac delta function be separated in spherical coordinates taking into account the

**u**(

**x**) dependence?