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ACOS(P) 			    POSIX Programmer's Manual				  ACOS(P)

       acos, acosf, acosl - arc cosine functions

       #include <math.h>

       double acos(double x);
       float acosf(float x);
       long double acosl(long double x);

       These  functions  shall compute the principal value of the arc cosine of their argument x.
       The value of x should be in the range [-1,1].

       An application wishing to check for error situations should set errno  to  zero	and  call
       feclearexcept(FE_ALL_EXCEPT)  before calling these functions.  On return, if errno is non-
       zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is	non-zero,
       an error has occurred.

       Upon successful completion, these functions shall return the arc cosine of x, in the range
       [0,pi] radians.

       For finite values of x not in the range [-1,1], a domain error shall occur, and	   either
       a NaN (if supported), or   an implementation-defined value shall be returned.

       If x is NaN, a NaN shall be returned.

       If x is +1, +0 shall be returned.

       If  x  is +-Inf, a domain error shall occur, and either a NaN (if supported), or an imple-
       mentation-defined value shall be returned.

       These functions shall fail if:

       Domain Error
	      The x argument is finite and is not in the range [-1,1],	  or is +-Inf.

       If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be
       set  to [EDOM]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
       then the invalid floating-point exception shall be raised.

       The following sections are informative.


       On  error,  the	expressions  (math_errhandling	&  MATH_ERRNO)	and  (math_errhandling	&
       MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.



       cos()  ,  feclearexcept()  ,  fetestexcept()  ,	isnan()  , the Base Definitions volume of
       IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for  Mathematical  Func-
       tions, <math.h>

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable	Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
       the Institute of Electrical and Electronics Engineers, Inc and  The  Open  Group.  In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					  ACOS(P)
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