ATAN (3)
arc tangent function
SYNOPSIS
#include <math.h>
double atan(double x );
DESCRIPTION
The atan() function calculates the arc tangent of x; that is
the value whose tangent is x.
RETURN VALUE
The atan() function returns the arc tangent in radians and the
value is mathematically defined to be between -PI/2 and PI/2
(inclusive).
CONFORMING TO
SVID 3, POSIX, BSD 4.3, ISO 9899
SEE ALSO
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