[Bug math/10716] New: various problems in cacosh and cacos

["zimmerma+gcc at loria dot fr" <sourceware-bugzilla at sourceware dot org>]

The classical branch cut for cacosh() is (-inf, 1). However, cacosh() is using
a different branch cut. For example (courtesy of Kaveh Ghazi):

cacosh(-1 + -0 I) -> (0 + 3.14159265358979 I)

With the classical branch cut, one would get (0 - 3.14159265358979 I).

Also the sign of 0 is not always correct:

cacos(1 + 0 I) -> (0 + 0 I) [should be (0 - O I)]

Finally the documentation of cacosh says that the real part of the result is
chosen non-negative, which is clearly wrong on this example:

cacosh(-3.45677995681763 + -2.3456699848175 I) -> (-2.11780021549476 +
2.53187508681341 I)

See
<http://lists.gforge.inria.fr/pipermail/mpc-discuss/2009-October/000581.html>
for more details.

-- 
           Summary: various problems in cacosh and cacos
           Product: glibc
           Version: 2.10
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: aj at suse dot de
        ReportedBy: zimmerma+gcc at loria dot fr
                CC: glibc-bugs at sources dot redhat dot com
 GCC build triplet: x86_64-redhat-linux
  GCC host triplet: x86_64-redhat-linux
GCC target triplet: x86_64-redhat-linux


http://sourceware.org/bugzilla/show_bug.cgi?id=10716

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