NAME    [Toc]    [Back]

     acos, acosf -- arc cosine functions

LIBRARY    [Toc]    [Back]

     Math Library (libm, -lm)

SYNOPSIS    [Toc]    [Back]

     #include <math.h>

     double
     acos(double x);

     float
     acosf(float x);

DESCRIPTION    [Toc]    [Back]

     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    [Toc]    [Back]

     The acos() and the acosf() functions return the arc cosine in the range
     [0, pi] radians.  On the VAX and Tahoe, if:

	   |x| > 1,

     acos(x) sets the global variable errno to EDOM and a reserved operand
     fault is generated.

SEE ALSO    [Toc]    [Back]

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

STANDARDS    [Toc]    [Back]

     The acos() function conforms to ISO/IEC 9899:1990 (``ISO C89'').


FreeBSD 5.2.1			  May 2, 1991			 FreeBSD 5.2.1