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acos(3)

NAME

     acos, acosf -- arc cosine functions

LIBRARY

     Math Library (libm, -lm)

SYNOPSIS

     #include <math.h>

     double
     acos(double x);

     float
     acosf(float x);

DESCRIPTION

     The acos() and the acosf() functions compute the principal value of the
     arc cosine of x.  A domain error occurs for arguments not in the range
     [-1, +1].	For a discussion of error due to roundoff, see math(3).

RETURN VALUES

     The acos() and the acosf() 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() function conforms to ISO/IEC 9899:1990 (``ISO C90'').

FreeBSD 5.4		       January 14, 2005 		   FreeBSD 5.4

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