# Homework Help: Using suffix notation to find alternative expressions

1. Oct 4, 2013

### ppy

1. The problem statement, all variables and given/known data
use the relationship ε$_{ijk}$ ε$_{klm}$=δ$_{il}$δ$_{jm}$-δ$_{im}$δ$_{jl}$ to find an alternative expression for ε$_{ijk}$ε$_{ilm}$. Hence simplify ε$_{ijk}$ε$_{ijm}$

2. Relevant equations

I know that the kronecker delta is 1 for i=j and 0 for i not equal to j. and that the alternating tensor is 0 for any I,j,k equal. +1 if (I,j,k)= (1,2,3) or (2,3,1) or (3,1,2) and -1 for (3,2,1) or (1,3,2) 0r (2,1,3). I also know that the alternating tensor is unchanged under cyclic permutations of its suffices. I know I am supposed to use all these facts but I am unsure how.

Help would be appreciated.

Thanks.

2. Oct 4, 2013

### tiny-tim

hi ppy!

in εijkεklm, the common index is 3rd and 1st

in εijkεilm, the common index is 1st and 1st

so use a cycllc permutation to make it 3rd and 1st