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  12 .TH acos 3M "12 Jul 2006" "SunOS 5.11" "Mathematical Library Functions"
  13 .SH NAME
  14 acos, acosf, acosl \- arc cosine functions
  15 .SH SYNOPSIS
  16 .LP
  17 .nf
  18 c99 [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
  19 #include <math.h>
  20 
  21 \fBdouble\fR \fBacos\fR(\fBdouble\fR \fIx\fR);
  22 .fi
  23 
  24 .LP
  25 .nf
  26 \fBfloat\fR \fBacosf\fR(\fBfloat\fR \fIx\fR);
  27 .fi
  28 
  29 .LP
  30 .nf
  31 \fBlong double\fR \fBacosl\fR(\fBlong double\fR \fIx\fR);
  32 .fi
  33 
  34 .SH DESCRIPTION
  35 .sp
  36 .LP
  37 These functions compute the principal value of the arc cosine of \fIx\fR. The
  38 value of \fIx\fR should be in the range [\(mi1,1].
  39 .SH RETURN VALUES
  40 .sp
  41 .LP
  42 Upon successful completion, these functions return the arc cosine of \fIx\fR in
  43 the range [0, \c
  44 .if n pi\c
  45 .if t \(*p
  46 \c
  47 ] radians.
  48 .sp
  49 .LP
  50 For finite values of  \fIx\fR not in the range [\(mi1,1], a domain error occurs
  51 and NaN is returned.
  52 .sp
  53 .LP
  54 If \fIx\fR is NaN, NaN is returned.
  55 .sp
  56 .LP
  57 If \fIx\fR is +1, +0 is returned.
  58 .sp
  59 .LP
  60 If \fIx\fR is \(+-Inf, a domain error occurs and NaN is returned.
  61 .sp
  62 .LP
  63 For exceptional cases, \fBmatherr\fR(3M) tabulates the values to be returned by
  64 \fBacos()\fR as specified by SVID3 and XPG3.
  65 .SH ERRORS
  66 .sp
  67 .LP
  68 These functions will fail if:
  69 .sp
  70 .ne 2
  71 .mk
  72 .na
  73 \fBDomain Error\fR
  74 .ad
  75 .RS 16n
  76 .rt  
  77 The \fIx\fR argument is finite and not in the range [-1,1], or is \(+-Inf.
  78 .sp
  79 If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
  80 non-zero, the invalid floating-point exception is raised.
  81 .sp
  82 The \fBacos()\fR function sets \fBerrno\fR to \fBEDOM\fR if \fIx\fR is not
  83 \(+-Inf or NaN and is not in the range [\(mi1,1].
  84 .RE
  85 
  86 .SH USAGE
  87 .sp
  88 .LP
  89 An application wanting to check for exceptions should call
  90 \fBfeclearexcept\fR(\fBFE_ALL_EXCEPT\fR) before calling these functions. On
  91 return, if \fBfetestexcept\fR(\fBFE_INVALID\fR | \fBFE_DIVBYZERO\fR |
  92 \fBFE_OVERFLOW\fR | \fBFE_UNDERFLOW\fR) is non-zero, an exception has been
  93 raised. An application should either examine the return value or check the
  94 floating point exception flags to detect exceptions.
  95 .sp
  96 .LP
  97 An application can also set \fBerrno\fR to 0 before calling \fBacos()\fR. On
  98 return, if \fBerrno\fR is non-zero, an error has occurred. The \fBacosf()\fR
  99 and \fBacosl()\fR functions do not set \fBerrno\fR.
 100 .SH ATTRIBUTES
 101 .sp
 102 .LP
 103 See \fBattributes\fR(5) for descriptions of the following attributes:
 104 .sp
 105 
 106 .sp
 107 .TS
 108 tab() box;
 109 cw(2.75i) |cw(2.75i) 
 110 lw(2.75i) |lw(2.75i) 
 111 .
 112 ATTRIBUTE TYPEATTRIBUTE VALUE
 113 _
 114 Interface StabilityStandard
 115 _
 116 MT-LevelMT-Safe
 117 .TE
 118 
 119 .SH SEE ALSO
 120 .sp
 121 .LP
 122 \fBcos\fR(3M), \fBfeclearexcept\fR(3M), \fBfetestexcept\fR(3M),
 123 \fBisnan\fR(3M), \fBmath.h\fR(3HEAD), \fBmatherr\fR(3M), \fBattributes\fR(5),
 124 \fBstandards\fR(5)