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From: "jsm28 at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug math/15023] New: cacos inaccurate for real part of result near
Date: Wed, 16 Jan 2013 23:04:00 -0000
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http://sourceware.org/bugzilla/show_bug.cgi?id=15023

             Bug #: 15023
           Summary: cacos inaccurate for real part of result near 0
           Product: glibc
           Version: 2.16
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: unassigned@sourceware.org
        ReportedBy: jsm28@gcc.gnu.org
    Classification: Unclassified


cacos is implemented as pi/2 - casin.  This leads to inaccurate results through
cancellation when the real part of the result of casin is near pi/2, so the
real part of the result of cacos is near 0.  For example, cacos (0x1p500 +
1.0i) gives a result with real part 0 (should be
3.054936363499604682051979393213617699789e-151).

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