dacosh

 Procedure Abstract Required_Reading Keywords Declarations Brief_I/O Detailed_Input Detailed_Output Parameters Exceptions Files Particulars Examples Restrictions Literature_References Author_and_Institution Version

#### Procedure

```  DACOSH ( Double precision arc hyperbolic cosine )

DOUBLE PRECISION FUNCTION  DACOSH ( X )

```

#### Abstract

```      Return the inverse hyperbolic cosine of a double
precision argument.
```

```     None.
```

#### Keywords

```      HYPERBOLIC,  MATH
```

#### Declarations

```
DOUBLE PRECISION   X

```

#### Brief_I/O

```      VARIABLE  I/O  DESCRIPTION
--------  ---  --------------------------------------------------
X         I   Number whose inverse hyperbolic cosine is desired.
X must be >= 1.
```

#### Detailed_Input

```      X      is any double precision number greater than or equal to 1.
```

#### Detailed_Output

```      DACOSH is the inverse hyperbolic cosine of X.
```

#### Parameters

```     None.
```

#### Exceptions

```      1) If X is less than 1.0d0, the error SPICE(INVALIDARGUMENT) is
signalled.
```

#### Files

```      None.
```

#### Particulars

```      This function simply implements the definition of the inverse
hyperbolic cosine as follows:

DACOSH = DLOG (X + DSQRT (X*X-1.D0))

If the input value is not valid, an error is signalled.
```

#### Examples

```      The following table gives a few values for X and the resulting
value of DACOSH.

X                       DACOSH(X)
----------------------------------------------
1.000000000000000      0.0000000000000000E+00
10.00000000000000       2.993222846126381
100.0000000000000       5.298292365610485
1000.000000000000       7.600902209541989
```

#### Restrictions

```      The value of the input variable X must be greater than or equal
to 1.0d0.
```

#### Literature_References

```      Any good book of mathematical tables and formulae, for example
Rubber Company.
```

#### Author_and_Institution

```      H.A. Neilan     (JPL)
W.M. Owen       (JPL)
```

#### Version

```     SPICELIB Version 1.1.0, 17-MAY-1994 (HAN)

Set the default function value to either 0, 0.0D0, .FALSE.,
or blank depending on the type of the function.

SPICELIB Version 1.0.1, 10-MAR-1992 (WLT)

Comment section for permuted index source lines was added
`Wed Apr  5 17:46:12 2017`