[dacoshresult,x]=dacosh(x);

function [dacoshresult,x]=dacosh(x);
dacoshresult=[];
persistent dln2 firstCall xmax ; if isempty(firstCall),firstCall=1;end; 

;
%***BEGIN PROLOGUE  DACOSH
%***PURPOSE  Compute the arc hyperbolic cosine.
%***LIBRARY   SLATEC (FNLIB)
%***CATEGORY  C4C
%***TYPE      doubleprecision (ACOSH-S, DACOSH-D, CACOSH-C)
%***KEYWORDS  ACOSH, ARC HYPERBOLIC COSINE, ELEMENTARY FUNCTIONS, FNLIB,
%             INVERSE HYPERBOLIC COSINE
%***AUTHOR  Fullerton, W., (LANL)
%***DESCRIPTION
%
% DACOSH(X) calculates the doubleprecision arc hyperbolic cosine for
% doubleprecision argument X.  The result is returned on the
% positive branch.
%
%***REFERENCES  (NONE)
%***ROUTINES CALLED  D1MACH, XERMSG
%***REVISION HISTORY  (YYMMDD)
%   770601  DATE WRITTEN
%   890531  Changed all specific intrinsics to generic.  (WRB)
%   890531  REVISION DATE from Version 3.2
%   891214  Prologue converted to Version 4.0 format.  (BAB)
%   900315  CALLs to XERROR changed to CALLs to XERMSG.  (THJ)
%***end PROLOGUE  DACOSH
if isempty(dln2), dln2=0; end;
if isempty(xmax), xmax=0; end;
if firstCall,   dln2=[0.69314718055994530941723212145818d0];  end;
if firstCall,   xmax=[0.0d0];  end;
firstCall=0;
%***FIRST EXECUTABLE STATEMENT  DACOSH
if( xmax==0.0d0 )
xmax = 1.0d0./sqrt(d1mach(3));
end;
%
if( x<1.0D0 )
xermsg('SLATEC','DACOSH','X LESS THAN 1',1,2);
end;
%
if( x<xmax )
dacoshresult = log(x+sqrt(x.*x-1.0d0));
end;
if( x>=xmax )
dacoshresult = dln2 + log(x);
end;
%
csnil=dbstack(1); csnil=csnil(1).name(1)~='@';
if csnil&&~isempty(inputname(1)), assignin('caller','FUntemp',x); evalin('caller',[inputname(1),'=FUntemp;']); end
end
%DECK DAIE