(no subject)

For integrals that depend on a parameter, and the output is a list of 
expressions for different cases of this parameter, how can properties on 
the parameter be included in the statement to get as output a single 
expression? Namely, in this example:

integrate(1/(x^2+a),x)

         2      +---+
       (x  - a)\|- a  + 2a x         +-+
   log(---------------------)      x\|a
                2             atan(-----)
               x  + a                a
  [--------------------------,-----------]
               +---+               +-+
             2\|- a               \|a
                               Type: Union(List Expression Integer,...)

tell to 'integrate' that a>0, say, and get the 'atan' expression.

I have read a few comments on the Axiom web sites about properties, provisos,
and a command 'Assume', eg here:

http://www.axiom-developer.org/axiom-website/currentstate.html

http://axiom-wiki.newsynthesis.org/DefiniteIntegration

But I have not found yet a hint on how to do it (if possible).

Alejandro Jakubi