# [Maxima] How to respond to question when using sum function

reyssat eric.reyssat at math.unicaen.fr
Wed May 13 01:32:44 CDT 2009

```Ellen Maki a écrit :
>
> Hello,
>
> I am a new user of maxima and have run into a difficulty. I wanted to
> sum the geometric series (because I know what the answer is and could
> use this to check that I’m using the function properly). These are the
> steps that I took:
>
> 1. From the toolbar, I first chose ‘Calculus’ and then selected
> ‘Calculate sum’
>
> 2. A ‘Sum’ dialogue box appeared. I entered p^(k-1) into the
> ‘expression’ box, k in the ‘variable’ box, 1 in the ‘from’ box, and 5
> in the ‘to’ box. I then put a check in the ‘simplify’ box and clicked OK.
>
> 3. A prompt then appeared on the screen: ‘Is abs(p)-1 positive,
> negative, or zero?’.
>
> 4. How do I enter a response? When I type a response after the prompt
> (ie negative), nothing happens. I can’t find anything in the
> documentation about how to respond to the question.
>
> Any help would be appreciated.
>
> Ellen
>
> ------------------------------------------------------------------------
>
>
Hello,

1/ I think the prompt with the question doesn't appear if you compute
the sum from 1 to 5, but only from 1 to inf, because then the answer
depends on the sign of abs(p)-1.

2/ giving an information to maxima (what to compute, or give anwer to
some maxima prompt) depends on your front end : xmaxima or wxmaxima. In
your case, it seems to be wxmaxima ; in that case, you execute a command
by typing SHIFT-ENTER (only ENTER if you use maxima).
Hence to answer your question in wxmaxima, just type p (or pos, or
positive) where the cursor is, and then SHIFT-ENTER.

I recommend using the 10 minute tutorial (or others) that you can find
here :
http://wxmaxima.sourceforge.net/wiki/index.php/Tutorials

Good luck

Eric Reyssat

```