Mathematica 9 is now available
Student Support Forum
Student Support Forum: 'How to write "Let a>0, ..."' topicStudent Support Forum > General > "How to write "Let a>0, ...""

Next Comment >Help | Reply To Topic
Author Comment/Response
Andreas Veh
09/10/00 12:38pm

Integrate[\[ExponentialE]^(-r/a), {r,0,\[Infinity]}]

yields an If[Re(a)>0, ...] . I know that I could use Abs[a] instead and would get the evaluated integral. But I have more problems of that sort where I need to tell it ''Let a>0, ...''. E.g.

Integrate[Exp[-r1]*r1^2*(Sqrt[(r1+r2)^2]-Sqrt[(r1-r2)^2])/r1/r2, {r1,0,Infinity}]

which is not evaluated.

The same integral can be rewritten: For r1<=r2, Integrate[Exp[-r1]*r1^2/r2, {r1,0,r2}] and for r1>=r2, Integrate[Exp[-r1], {r1,r2,Infinity}] which are evaluated. But how do I tell Mathematica ''For r1<=r2, Integrate[Exp[-r1]*r1^2*(Sqrt[(r1+r2)^2]-Sqrt[(r1-r2)^2])/r1/r2, {r1,0,r2}]'' etc.?

URL: ,

Subject (listing for 'How to write "Let a>0, ..."')
Author Date Posted
How to write "Let a>0, ..." Andreas Veh 09/10/00 12:38pm
Re: How to write Ricardo 06/11/02 07:12am
Next Comment >Help | Reply To Topic