ATANSection: Linux Programmer's Manual (3)
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NAMEatan, atanf, atanl - arc tangent function
#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)):
DESCRIPTIONThe atan() function calculates the principal value of the arc tangent of x; that is the value whose tangent is x.
RETURN VALUEOn 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.
ERRORSNo errors occur.
CONFORMING TOC99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.
SEE ALSOacos(3), asin(3), atan2(3), carg(3), catan(3), cos(3), sin(3), tan(3)
COLOPHONThis page is part of release 3.21 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/.