# Matrix representation for (S1+S2)^2 operator

1. Apr 6, 2007

### martina

Last edited: Apr 7, 2007
2. Apr 7, 2007

### martina

I've derived the matrix using two different, but equivalent methods (the one described in the above link-Sakurai and by calculating the direct products of Pauli matrices) and it came out the same, yet its eigenvalues are not what I know they must be, so there must be something fundamentally wrong in my procedure, but I just can't detect it. If you happen to know how the matrix looks like without a detailed derivation, I'd be grateful for that too, cause I'm really stuck here