Hi, eveyone have been struggling to do this problem for a long time now, figured it is something very simple I am missing so thought I should ask here. 1. The problem statement, all variables and given/known data Parker's solar wind equation is given after some manipulation as: (v - (Cs2 / v) dv/dr = 2 (Cs2 / r2) (r - rc ) where rc = GMm/4kT (the critical radius) and Cs2 = 2kT/m (coronal sound speed) 3. The attempt at a solution So using the usual method I separate the variables and integrate this equation to get: v2 / 2 - Cs2 log(v) = 2Cs2 log(r) + (4Cs2 rc / r) + C where C is the constant of integration. However every solution However every solution I see around the internet and indeed in my notes quotes the solution: (v2 / Cs2) - log(v2/ Cs2) = 4log(r/rc) + 4(r/rc) and I cannot seem to figure out why. Am I missing something blindingly obvious here? Thanks for your time, John.