freebsd man page for acos

ACOS(3) 						   BSD Library Functions Manual 						   ACOS(3)

NAME
     acos, acosf, acosl -- arc cosine functions

LIBRARY
     Math Library (libm, -lm)

SYNOPSIS
     #include <math.h>

     double
     acos(double x);

     float
     acosf(float x);

     long double
     acosl(long double x);

DESCRIPTION
     The acos(), acosf(), and acosl() functions compute the principal value of the arc cosine of x.

RETURN VALUES
     These functions return the arc cosine in the range [0, pi] radians.  If:

	   |x| > 1,

     acos(x) raises an invalid exception and returns an NaN.

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

STANDARDS
     The acos(), acosf(), and acosl() functions conform to ISO/IEC 9899:1999 (``ISO C99'').

BSD
								   July 31, 2008							       BSD