 
      DOUBLE PRECISION FUNCTION DACOSH(X)
C***BEGIN PROLOGUE  DACOSH
C***DATE WRITTEN   770601   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  C4C
C***KEYWORDS  DOUBLE PRECISION,ELEMENTARY FUNCTION,
C             INVERSE HYPERBOLIC COSINE
C***AUTHOR  FULLERTON, W., (LANL)
C***PURPOSE  Computes the arc hyperbolic Cosine.
C***DESCRIPTION
C
C DACOSH(X) calculates the double precision arc hyperbolic cosine for
C double precision argument X.  THe result is returned on the
C positive branch.
C***REFERENCES  (NONE)
C***ROUTINES CALLED  D1MACH,XERROR
C***END PROLOGUE  DACOSH
 
 
