1. The problem statement, all variables and given/known data This is going to be confusing to read, as I don't know how to make this look right. The first integral is from 0 to L-2d, the second from x1+d to L-d, and the third from x2 to L. (F(x)=1) 1.) 0[tex]\int[/tex]L-2d,x1+d[tex]\int[/tex]L-d,x2+d[tex]\int[/tex]L dx3dx2dx1 2.) 0[tex]\int[/tex]L-2d,x1+d[tex]\int[/tex]L-d (L-x2-d)dx2dx1 3.) substituting y2 for L-x2-d 4.) 0[tex]\int[/tex]L-2d,0[tex]\int[/tex]L-X1-2d y2dy2dx1 2. Relevant equations 3. The attempt at a solution The answer to this isn't that important, as I already have the solution. What I don't understand is why after substituting y2, the upper and lower bounds of the corresponding integral aren't the other way around, with L-x1-2d the lower bound, and 0 the upper. Is this because dy2=-dx2? Probably, but I just want to make sure I understand what's going on.