Subject: integrate 'quotient by zero' error message
From: Panagiotis Papasotiriou
Date: Sun, 30 Oct 2011 02:07:00 +0300
2011/10/30 Edwin Woollett <woollett at charter.net>
> I'm guessing the integrate code finds divide by
> zero here?
>
> The "quotient by zero" error message seems
> unclear English.
> ----------------------
>
Integrand's denominator is obviously nonzero for any x within the
integration interval. If I were to guess, I'd say that Maxima tries to
compute the indefinite integral first, doing a transformation maybe.
Somewhere there the error message is generated, no idea why.
> (%i25) integrate(sin(x+sqrt(x))/(1+x)**,x,0,inf);
>
> `quotient' by `zero'
>
> -- an error. To debug this try: debugmode(true);
>
Integral is probably divergent; It seems that Integral value is oscillating
around ~0.458 and never converges. This doesn't explain the error message
though.
> (%i26) integrate(sin(x+sqrt(x))/(1+x)**,x,0,10);
>
> `quotient' by `zero'
>
> -- an error. To debug this try: debugmode(true);
>
I wouldn't even try integrate() with such an integrand, to be honest.
Integral for x in [0,10] can be easily computed by quad_quags and it is
~0.3911.
> (%i27) integrate(sin(x+sqrt(x))/(1+x)**,x);
>
> `quotient' by `zero'
>
> -- an error. To debug this try: debugmode(true);
>
Indefinite integral cannot be computed analytically, but that doesn't
explain why Maxima gives that error message. However, it seems the error
message is generated before any try to compute the integral numerically, as
I guessed.