atan (3)
NAME
atan, atanf, atanl - arc tangent functionSYNOPSIS
#include <math.h> double atan(double x);Link with -lm.
float atanf(float x);
long double atanl( long double x);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
atanf(), atanl():
-
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
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
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