I can't understand start from the second page (solve for C1&C2), how it comes out(need detail steps, my math is not well), and why the following part looks like this?(Write Q=T/R, then R becomes that equation, I don't know how it transfer from the above equation)

I need detail explain and process step by step please, thanks!

sistance in series: 2Lk2n(r3/r2)+R.ut Solve for c1&c2 c1=hln(RR+)+R+kih(TairT0)c2=hln(RR+)+R+kih{T0ln(R+)TairlnR}+R+kiT0 Q=z=0L=02(kirTr=R+srdzd)=2kiLc1 Write =RT s.t. R=2Lkiln(RR+)+2(R+)Lh1 R=R() conduction convection increases, so does conduct" resistance resistance. sistance while convection res. I decrease. This implies existence T an optimum which corresponds to alance. This value of will maximise heat loss. Q=0;solveforoptimum=hkiR