How can I get an answer in real terms?
$Assumptions = (x|y|z|a|b|c)\[Element] Reals p:=Sqrt[(a-x)^2+(b-y)^2+(c-z)^2] I1a= Integrate[a/p,b]//FullSimplify I2a =Integrate[I1a,c]//FullSimplify
This combination gives a real expression:
Simplify[ComplexExpand@Simplify[I2a // TrigToExp, {a > x, b > y, c > z}] /. Arg[u_] :> ArcTan[ComplexExpand[Im[u]/Re[u]]]]
Thank you. It works really well.