kron[m_,n_]:=\!\( \*SubsuperscriptBox[\(\[Integral]\), \(0\), \(2\)]\(\(Sin[ \*FractionBox[\(n\ \[Pi]\ x\), \(2\)]]\ Sin[ \*FractionBox[\(m\ \[Pi]\ x\), \(2\)]]\) \[DifferentialD]x\)\) This is the integral over x of sin(n pi x / 2) times sin(m pi x / 2) from 0 to 2. This is one way to define the Kronecker Delta function. Given m and n as integers and not both zero, if m = n then the output is 1, if m ≠ n the output is 0. Why then is it that when I type: Simplify[kron[m, n], Element[m, Integers] && Element[n, Integers]] that I get zero? If I do kron[1, 1] I get 1! How can Mathematica say a function is 0 over the integers when I just put in two integers and got a non-zero ouput? It is certainly not identical to zero right?