Maybe it's a dumb question, but I'm trying to understand some tensor/kronecker calculations that are something off-course :
Calculate the expressions :
$$δ_{ik}u_k,δ_{ij}δ_{ij}$$
So :
$$δ_{ik}u_k = u_i = u_1 + u_2 + u_3$$
$$δ_{ij}δ_{ij} = δ_{jj} = δ_{ii} = δ_{11} + δ_{22} + δ_{33} = 3$$
What I wanted to ask, is why does the solver always chose to go until the number $i=3$ ?