- #1
ENgez
- 75
- 0
In the attached equation from structural analysis, I don't understand the transition between the second and third equal signs. I think that [itex] u_{j,l}da_l = u_{j,1}da_1+u_{j,2}da_2+u_{j,3}da_3 [/itex], so doesn't equating [itex]da_j\delta_{lj} = da_l [/itex] assume that [itex] l=j [/itex]. can anyone help me see why this assumption is justified?