SIMPLE SOLUTIONS

ATAN2, ATAN2F, ATAN2L - reference manual online

Arc tangent function of two variables.

Chapter
2015-04-19
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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc -std=c99
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 tangent of y/x in radi‐ ans; 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 infinity, +pi (-pi) is returned. If y is a finite value greater (less) than 0, and x is positive infinity, +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 infinity, +3*pi/4 (-3*pi/4) is returned. If y is positive infinity (negative infinity) and x is positive infinity, +pi/4 (-pi/4) is returned.
ERRORS No errors occur.
ATTRIBUTES For an explanation of the terms used in this section, see attributes(7). ┌─────────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├─────────────────────────────┼───────────────┼─────────┤ │atan2(), atan2f(), atan2l() │ 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 4.04 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 http://www.kernel.org/doc/man-pages/.
2015-04-19 ATAN2(3)
This manual Reference Other manuals
atan2(3) referred by acos(3) | asin(3) | atan(3) | cos(3) | sin(3) | tan(3)
refer to acos(3) | asin(3) | atan(3) | attributes(7) | carg(3) | cos(3) | feature_test_macros(7) | sin(3) | tan(3)