osx man page for atanl

ATAN(3) 						   BSD Library Functions Manual 						   ATAN(3)

NAME
     atan -- arc tangent function of one variable

SYNOPSIS
     #include <math.h>

     double
     atan(double x);

     long double
     atanl(long double x);

     float
     atanf(float x);

DESCRIPTION
     The atan() function computes the principal value of the arc tangent of x.	The result is in the range [-pi/2, +pi/2].

SPECIAL VALUES
     atan(+-0) returns +-0.

     atan(+-infinity) returns +-pi/2

VECTOR OPERATIONS
     If you need to apply the atan() function to SIMD vectors or arrays, using the following functions provided by the Accelerate.framework may
     give significantly better performance:

     #include <Accelerate/Accelerate.h>

     vFloat vatanf(vFloat x);
     void vvatanf(float *y, const float *x, const int *n);
     void vvatan(double *y, const double *x, const int *n);

SEE ALSO
     acos(3), asin(3), atan2(3), cos(3), cosh(3), sin(3), sinh(3), tan(3), tanh(3), math(3) The atan() function conforms to ISO/IEC 9899:2011.

BSD
								 December 11, 2006							       BSD