CFLib.org – Common Function Library Project

Description:
Returns the inverse hyberbolic tangent of a value. All angles are expressed in radians.

Return Values:
Returns an angle in radians.

Example:

<CFSET x=0.5>
  <CFOUTPUT>
  Given x=0.5<BR>
  The Atanh of #x# is: #Atanh(x)# radians
  </CFOUTPUT>

Parameters:

Full UDF Source:

/**
 * Returns the inverse hyberbolic tangent of a value.
 * 
 * @param x      Real number < 1.0 
 * @return Returns an angle in radians. 
 * @author Joel Cox (jlcox@goodyear.com) 
 * @version 1, November 29, 2001 
 */
function Atanh(x)
{
  Var RetVal = 0;
  Var Neg = False;
  if (x LTE 1.0) 
    RetVal = 0.0;
  else
    if (x LT 0) 
          Neg = True;
    x = Abs(x);
    if (X GTE 1)
      RetVal = "overflow";
    else
      RetVal = 0.5 * Log(((2.0 * x) / (1.0 - x)) + 1);
    if (Neg) 
        RetVal = -RetVal;
  Return(RetVal);
}