#1529 unsimplified result from rectform

closed
nobody
None
5
2012-12-04
2008-11-16
No

(%i1) logarc : true;
(%o1) true

(%i2) rectform(log(x + %i * y));
(%o2) log(y^2+x^2)/2+%i*atan2(y,x)

(%i3) expand(%,0,0);
(%o3) log(y^2+x^2)/2+(log((%i*y)/x+1)-log(1-(%i*y)/x))/2

Also (%o3) is wrong for x = 0 and in the left half plane.

Discussion

  • Dieter Kaiser

    Dieter Kaiser - 2009-05-08
    • milestone: --> Includes_proposed_fix
     
  • Dieter Kaiser

    Dieter Kaiser - 2009-05-08

    The expression does not simplify as expected because the global flag $logarc is set to nil in the routine risplit. It is possible to remove this from the routine risplit. Then we would get:

    (%i11) rectform(log(x+%i*y)),logarc;
    (%o11) log((%i*y+x)/sqrt(y^2+x^2))+log(y^2+x^2)/2

    Because of revision 1.25 the result of the simplification is now correct.

    I have checked this with the testsuite and the share_testsuite. There are no examples which depend on the setting of $logargs in the routine risplit.

    Should we change the routine risplit and remove the setting of the flag $logarg?

    Dieter Kaiser

     
  • Dieter Kaiser

    Dieter Kaiser - 2009-11-30

    As discussed on the mailing list, rectform sets the option variable logarc to NIL to preserve the standard form x+%i*y for its result.

    With Maxima 5.19post we get:

    (%i4) rectform(log(x+%i*y));
    (%o4) log(y^2+x^2)/2+%i*atan2(y,x)

    logarc gives the following result, which no longer has the standard form of rectform:

    (%i5) logarc(%);
    (%o5) log((%i*y+x)/sqrt(y^2+x^2))+log(y^2+x^2)/2

    I think we can close this bug report. The first issue has gone. The result of rectform is correct. The second issue is the expected behavior. rectform returns a standard form, which might simplify further, when the user sets the option variable logarc to TRUE.

    Setting the status to pending and the resolution to "works for me".

    Dieter Kaiser

     
  • Dieter Kaiser

    Dieter Kaiser - 2009-11-30
    • status: open --> pending
     
  • SourceForge Robot

    This Tracker item was closed automatically by the system. It was
    previously set to a Pending status, and the original submitter
    did not respond within 14 days (the time period specified by
    the administrator of this Tracker).

     
  • SourceForge Robot

    • status: pending --> closed
     

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