table of contents
ATAN(3) | Linux Programmer's Manual | ATAN(3) |
NAME¶
atan, atanf, atanl - arc tangent function
SYNOPSIS¶
#include <math.h> double atan(double x);
float atanf(float x);
long double atanl( long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
atanf(), atanl():
or cc -std=c99
DESCRIPTION¶
The atan() function calculates the principal value of the arc tangent of x; that is the value whose tangent is x.
RETURN VALUE¶
On success, these functions return the principal value of the arc tangent of x in radians; the return value is in the range [-pi/2, pi/2].
If x is a NaN, a NaN is returned.
If x is +0 (-0), +0 (-0) is returned.
If x is positive infinity (negative infinity), +pi/2 (-pi/2) is returned.
ERRORS¶
No errors occur.
CONFORMING TO¶
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.
SEE ALSO¶
acos(3), asin(3), atan2(3), carg(3), catan(3), cos(3), sin(3), tan(3)
COLOPHON¶
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.
2010-09-20 |