I have a function, S[q] which is obtained by integrating another function, A[r,q] over r. My problem is that the lower limit of integration, rmin depends on q in a complicated manner. Mathematica can however solve this equation to give several routes, only one of which is real which is the one I want. I have a second function too, L[q] which is also obtained by integrating B[r,q] over r. Again the lower limit of integration depends on q in the same manner. What I want to do is for a given value of q, solve the equation for rmin, and use this to calculate the corresponding L[q]. I then wish to calculate S[q] in the same manner. I want Mathematica to do this for many values of q over a range and use the results to plot S[q] against L[q]. Does anyone know an efficient way to do this? Thank you for your help.