GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


man:atan2f

ATAN2(3) Linux Programmer's Manual ATAN2(3)

NAME

     atan2, atan2f, atan2l - arc tangent function of two variables

SYNOPSIS

     #include <math.h>
     double atan2(double y, double x);
     float atan2f(float y, float x);
     long double atan2l(long double y, long double x);
     Link with -lm.
 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
     atan2f(), atan2l():
            _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
                || /* Since glibc 2.19: */ _DEFAULT_SOURCE
                || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

     These functions calculate the principal value of  the  arc  tangent  of
     y/x,  using the signs of the two arguments to determine the quadrant of
     the result.

RETURN VALUE

     On success, these functions return the principal value of the arc  tan-
     gent of y/x in radians; the return value is in the range [-pi, pi].
     If y is +0 (-0) and x is less than 0, +pi (-pi) is returned.
     If y is +0 (-0) and x is greater than 0, +0 (-0) is returned.
     If y is less than 0 and x is +0 or -0, -pi/2 is returned.
     If y is greater than 0 and x is +0 or -0, pi/2 is returned.
     If either x or y is NaN, a NaN is returned.
     If y is +0 (-0) and x is -0, +pi (-pi) is returned.
     If y is +0 (-0) and x is +0, +0 (-0) is returned.
     If  y is a finite value greater (less) than 0, and x is negative infin-
     ity, +pi (-pi) is returned.
     If y is a finite value greater (less) than 0, and x is positive  infin-
     ity, +0 (-0) is returned.
     If  y  is  positive infinity (negative infinity), and x is finite, pi/2
     (-pi/2) is returned.
     If y is positive infinity (negative infinity) and x is negative  infin-
     ity, +3*pi/4 (-3*pi/4) is returned.
     If  y is positive infinity (negative infinity) and x is positive infin-
     ity, +pi/4 (-pi/4) is returned.

ERRORS

     No errors occur.

ATTRIBUTES

     For  an  explanation  of  the  terms  used   in   this   section,   see
     attributes(7).
     allbox;  lbw28  lb  lb  l  l  l.  Interface Attribute Value T{ atan2(),
     atan2f(), atan2l() T}   Thread safety  MT-Safe

CONFORMING TO

     C99, POSIX.1-2001, POSIX.1-2008.
     The variant returning double also conforms to SVr4, 4.3BSD, C89.

SEE ALSO

     acos(3), asin(3), atan(3), carg(3), cos(3), sin(3), tan(3)

COLOPHON

     This page is part of release 4.16 of the Linux  man-pages  project.   A
     description  of  the project, information about reporting bugs, and the
     latest    version    of    this    page,    can     be     found     at
     https://www.kernel.org/doc/man-pages/.
                                2017-09-15                          ATAN2(3)
/data/webs/external/dokuwiki/data/pages/man/atan2f.txt · Last modified: 2019/05/17 09:47 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki