Subject: help with evaluation of expression [newbie]
From: Panagiotis Papasotiriou
Date: Wed, 26 Oct 2011 12:53:36 +0300
2011/10/26 Hugo Coolens <coolens at kahosl.be>
> I thought the following expression would evaluate as U_B, but it doesn't
>
> limit((1/T)*integrate(U_B*(1-**e^(-t/tau)), t, 0, T),T,inf,plus);
>
> maybe someone here can tell me how to proceed correctly.
>
> thanks in advance
> hugo
>
You are missing a "%" before "e^(-t/tau)", and thus Maxima treats e as an
arbitrary variable, not the mathematical constant e=2.71828... Use
limit((1/T)*integrate(U_B*(1-%e^(-t/tau)), t, 0, T),T,inf,plus);
Maxima will then ask you if tau is positive or negative; Answer "positive",
and you will get the result you are looking for. Another way is to type:
assume(tau>0);
limit((1/T)*integrate(U_B*(1-%e^(-t/tau)), t, 0, T),T,inf,plus);
so that you won't asked about tau.