You should read the whole article, in which mysum is described and defined
on page 10.
> -----Original Message-----
> From: maxima-bounces at math.utexas.edu
> [mailto:maxima-bounces at math.utexas.edu] On Behalf Of Shahir Molaei
> Sent: Tuesday, March 18, 2008 9:45 PM
> To: maxima at math.utexas.edu
> Subject: Re: [Maxima] Matrices of indefinite size
>
> But the use of 'mysum' also returns the 'false' output. Is
> 'mysum' a built-in function or I should define it somewhere?
> [Of course my ignorance is a direct consequense of my ignorance]