Mathematical Library Functions                           acos(3M)



NAME
     acos, acosf, acosl - arc cosine functions

SYNOPSIS
     c99 [ flag... ] file... -lm [ library... ]
     #include 

     double acos(double x);


     float acosf(float x);


     long double acosl(long double x);


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

RETURN VALUES
     Upon successful completion, these functions 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 occurs and NaN is returned.


     If x is NaN, NaN is returned.


     If x is ]1, ]0 is returned.


     If x is ]Inf, a domain error occurs and NaN is returned.


     For exceptional cases, matherr(3M) tabulates the  values  to
     be returned by acos() as specified by SVID3 and XPG3.

ERORS
     These functions will fail if:

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

                     If the integer expression  (matherrhandling
                     &  MATHEREXCEPT)  is non-zero, the invalid
                     floating-point exception is raised.

                     The acos() function sets errno to EDOM if  x



SunOS 5.11          Last change: 12 Jul 2006                    1






Mathematical Library Functions                           acos(3M)



                     is  not  ]Inf or NaN and is not in the range
                     [-1,1].


USAGE
     An application wanting to check for exceptions  should  call
     feclearexcept(FEALEXCEPT) before calling these functions.
     On  return,  if  fetestexcept(FEINVALID    FEDIVBYZERO  
     FEOVERFLOW    FEUNDERFLOW)  is non-zero, an exception has
     been raised. An application should either examine the return
     value  or check the floating point exception flags to detect
     exceptions.


     An application can  also  set  errno  to  0  before  calling
     acos().  On  return,  if  errno  is  non-zero,  an error has
     occurred. The acosf()  and  acosl()  functions  do  not  set
     errno.

ATRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     
           ATRIBUTE TYPE               ATRIBUTE VALUE       
    
     Interface Stability          Standard                    
    
     MT-Level                     MT-Safe                     
    


SEE ALSO
     cos(3M),  feclearexcept(3M),  fetestexcept(3M),   isnan(3M),
     math.h(3HEAD), matherr(3M), attributes(5), standards(5)


















SunOS 5.11          Last change: 12 Jul 2006                    2