#547 integrate(1/(x+a),x) missing abs

closed
nobody
Lisp Core (471)
5
2005-08-22
2004-04-02
Anonymous
No

presently integrate(1/(x+a),x) returns log(x+a)
It should return log(abs(x + a))

Discussion

  • Stavros Macrakis

    • summary: integrate(1/(x+a),x) is incomplete --> integrate(1/(x+a),x) missing abs
     
  • Barton Willis

    Barton Willis - 2004-04-09

    Logged In: YES
    user_id=570592

    On the reals integrate(1/x,x) == log(abs(x)) is okay, but on
    the complex plane, it's wrong. For one, abs isn't differentiable
    anywhere in the complex plane. If you run into a problem and
    think you need log(abs( .... )), try logcontract.

    Barton

     
  • Barton Willis

    Barton Willis - 2004-09-07

    Logged In: YES
    user_id=895922

    When the logabs == true, you get the value you want.
    I'll change the status of this bug to 'resolved.'

    (%i1) integrate(1/(x+a),x), logabs : false;
    (%o1) LOG(x + a)
    (%i2) integrate(1/(x+a),x), logabs : true;
    (%o2) LOG(ABS(x + a))
    (%i3) build_info();

    Maxima version: 5.9.0.9beta2
    Maxima build date: 7:39 9/1/2004
    host type: i686-pc-mingw32
    lisp-implementation-type: Kyoto Common Lisp
    lisp-implementation-version: GCL 2.6.5

    Barton

     
  • Robert Dodier

    Robert Dodier - 2005-08-22
    • status: open --> closed
    • labels: --> Lisp Core
     
  • Robert Dodier

    Robert Dodier - 2005-08-22

    Logged In: YES
    user_id=501686

    Closing this report as "Won't fix" since it's apparently not
    a bug according to discussion below.

     

Log in to post a comment.