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  10 .TH acosh 3M "12 Jul 2006" "SunOS 5.11" "Mathematical Library Functions"
  11 .SH NAME
  12 acosh, acoshf, acoshl \- inverse hyperbolic cosine functions
  13 .SH SYNOPSIS
  14 .LP
  15 .nf
  16 c99 [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
  17 #include <math.h>
  18 
  19 \fBdouble\fR \fBacosh\fR(\fBdouble\fR \fIx\fR);
  20 .fi
  21 
  22 .LP
  23 .nf
  24 \fBfloat\fR \fBacoshf\fR(\fBfloat\fR \fIx\fR);
  25 .fi
  26 
  27 .LP
  28 .nf
  29 \fBlong double\fR \fBacoshl\fR(\fBlong double\fR \fIx\fR);
  30 .fi
  31 
  32 .SH DESCRIPTION
  33 .sp
  34 .LP
  35 These functions compute the inverse hyperbolic cosine of their argument
  36 \fIx\fR.
  37 .SH RETURN VALUES
  38 .sp
  39 .LP
  40 Upon successful completion, these functions return the inverse hyperbolic
  41 cosine of their argument.
  42 .sp
  43 .LP
  44 For finite values of  \fIx\fR < 1, a domain error occurs and NaN is returned.
  45 .sp
  46 .LP
  47 If \fIx\fR is NaN, NaN is returned.
  48 .sp
  49 .LP
  50 If \fIx\fR is +1, +0 is returned.
  51 .sp
  52 .LP
  53 If \fIx\fR is +Inf, +Inf is returned.
  54 .sp
  55 .LP
  56 If \fIx\fR is \(miInf, a domain error occurs and NaN is returned.
  57 .sp
  58 .LP
  59 For exceptional cases, \fBmatherr\fR(3M) tabulates the values to be returned by
  60 \fBacosh()\fR as specified by SVID3 and XPG3.
  61 .SH ERRORS
  62 .sp
  63 .LP
  64 These functions will fail if:
  65 .sp
  66 .ne 2
  67 .mk
  68 .na
  69 \fBDomain Error\fR
  70 .ad
  71 .RS 16n
  72 .rt  
  73 The \fIx\fR argument is finite and less than 1.0, or is \(miInf.
  74 .sp
  75 If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
  76 non-zero, the invalid floating-point exception is raised.
  77 .sp
  78 The \fBacosh()\fR function sets \fBerrno\fR to \fBEDOM\fR if \fIx\fR is less
  79 than 1.0.
  80 .RE
  81 
  82 .SH USAGE
  83 .sp
  84 .LP
  85 An application wanting to check for exceptions should call
  86 \fBfeclearexcept\fR(\fBFE_ALL_EXCEPT\fR) before calling these functions. On
  87 return, if \fBfetestexcept\fR(\fBFE_INVALID\fR | \fBFE_DIVBYZERO\fR |
  88 \fBFE_OVERFLOW\fR | \fBFE_UNDERFLOW\fR) is non-zero, an exception has been
  89 raised. An application should either examine the return value or check the
  90 floating point exception flags to detect exceptions.
  91 .sp
  92 .LP
  93 An application can also set \fBerrno\fR to 0 before calling \fBacosh()\fR. On
  94 return, if \fBerrno\fR is non-zero, an error has occurred. The \fBacoshf()\fR
  95 and \fBacoshl()\fR functions do not set \fBerrno\fR.
  96 .SH ATTRIBUTES
  97 .sp
  98 .LP
  99 See \fBattributes\fR(5) for descriptions of the following attributes:
 100 .sp
 101 
 102 .sp
 103 .TS
 104 tab() box;
 105 cw(2.75i) |cw(2.75i) 
 106 lw(2.75i) |lw(2.75i) 
 107 .
 108 ATTRIBUTE TYPEATTRIBUTE VALUE
 109 _
 110 Interface StabilityStandard
 111 _
 112 MT-LevelMT-Safe
 113 .TE
 114 
 115 .SH SEE ALSO
 116 .sp
 117 .LP
 118 \fBcosh\fR(3M), \fBfeclearexcept\fR(3M), \fBfetestexcept\fR(3M),
 119 \fBmath.h\fR(3HEAD), \fBmatherr\fR(3M), \fBattributes\fR(5), \fBstandards\fR(5)