# [Maxima] Strange error

Raymond Toy (RT/EUS) raymond.toy at ericsson.com
Thu Mar 13 13:32:28 CDT 2008

```Rene Grothmann wrote:
> Why is
>
> integrate(exp(t)*(1+t^2),t,0,a)
>
> asking, if a is negative, zero, or positive? However
>
> integrate(exp(t)*(1+t^2),t,a,b)
>
> works.
>

The short answer is that maxima needs to know to figure out how to do
the integral. :-)

In the first case, it wants to know if it can transform the integral
from 0 to a into the range 0 to 1, and also if the integrand has a
certain form.  This form only works if the upper limit is positive.  In
this particular example, the integrand has the wrong form, so the
transformation can't be used anyway.

After that, a different method is tried, which is the same method that
is used directly for the second integral, since the lower limit isn't 0.

I suppose the test could be changed to check for the form of the
integrand before checking for the sign of the upper limit.  Might fix
this, but might introduce other issues.

Ray
```