- #1

- 2

- 0

(a) ∫

*d*

**Ω**Ω

*i*Ω

*j*= 4π/3 δ

*ij*;

*i*,

*j = x*,

*y*,

*z*;

4π

(b) ∫

*d*

**Ω**Ω

*x*Ω

*y*Ω

*z*= 0, if

*l*,

*m*, or

*n*is odd.

4π

The integrals are over 4π.

This is part of the derivation of the diffusion equation from the neutron transport equation. Part (b) from D&H Next note that the integral of the product of any odd number of components of OMEGA vanishes by symmetry.

(a) I think that 4π/3 comes from the volume of the sphere and δ

*ij is the kronecker delta. I don't know how to show this mathematically.*

(b)I think that this has to do with the sin or cos function.

(b)