freebsd man page for atan

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

NAME
     atan, atanf, atanl -- arc tangent functions of one variable

LIBRARY
     Math Library (libm, -lm)

SYNOPSIS
     #include <math.h>

     double
     atan(double x);

     float
     atanf(float x);

     long double
     atanl(long double x);

DESCRIPTION
     The atan(), atanf(), and atanl() functions compute the principal value of the arc tangent of x.

RETURN VALUES
     These functions return the arc tangent in the range [-pi/2, +pi/2] radians.

SEE ALSO
     acos(3), asin(3), atan2(3), cos(3), cosh(3), math(3), sin(3), sinh(3), tan(3), tanh(3)

STANDARDS
     The atan(), atanf(), and atanl() functions conform to ISO/IEC 9899:1999 (``ISO C99'').

BSD
								   July 31, 2008							       BSD