 
      DOUBLE PRECISION FUNCTION DATANH(X)
C***BEGIN PROLOGUE  DATANH
C***DATE WRITTEN   770601   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  C4C
C***KEYWORDS  DOUBLE PRECISION,ELEMENTARY FUNCTION,
C             INVERSE HYPERBOLIC TANGENT
C***AUTHOR  FULLERTON, W., (LANL)
C***PURPOSE  Computes the d.p. arc hyperbolic Tangent.
C***DESCRIPTION
C
C DATANH(X) calculates the double precision arc hyperbolic
C tangent for double precision argument X.
C
C Series for ATNH       on the interval  0.          to  2.50000E-01
C                                        with weighted error   6.86E-32
C                                         log weighted error  31.16
C                               significant figures required  30.00
C                                    decimal places required  31.88
C***REFERENCES  (NONE)
C***ROUTINES CALLED  D1MACH,DCSEVL,INITDS,XERROR
C***END PROLOGUE  DATANH
 
 
