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Synopsis:
    #include <math.h>
    double acosh( double x );

Description:
    The acosh function computes the inverse hyperbolic cosine of x.  A
    domain error occurs if the value of x is less than 1.0.

Returns:
    The acosh function returns the inverse hyperbolic cosine value.  When
    the argument is outside the permissible range, the  matherr function is
    called.  Unless the default  matherr function is replaced, it will set
    the global variable  errno to  EDOM, and print a "DOMAIN error"
    diagnostic message using the  stderr stream.

Example:
    #include <stdio.h>
    #include <math.h>

    void main()
      {
        printf( "%f\n", acosh( 1.5 ) );
      }

    produces the following:

    0.962424

Classification:
    WATCOM

Systems:
    Math

See Also:
    asinh, atanh, cosh, matherr