ACOS(3)                     BSD Programmer's Manual                    ACOS(3)

NAME
     acos - arc cosine function

SYNOPSIS
     #include <math.h>

     double
     acos(double x)

DESCRIPTION
     The acos() function computes 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() function returns 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
     sin(3),  cos(3),  tan(3),  asin(3),  atan(3),  atan2(3),  sinh(3),
     cosh(3),  tanh(3),  math(3),

STANDARDS
     The acos() function conforms to ANSI C3.159-1989 (``ANSI C'').

BSDI BSD/386                    March 26, 1993                               1