D9ATN1(3)

SYNOPSIS
DOUBLE PRECISION FUNCTION D9ATN1 (X)

NAME
d9atn1 - Evaluate DATAN(X) from first order relative accuracy so that DATAN(X) = X + X**3*D9ATN1(X).

LIBRARY
SLATEC (FNLIB)

CATEGORY
C4A

TYPE
DOUBLE PRECISION (R9ATN1-S, D9ATN1-D)

KEYWORDS
ARC TANGENT, ELEMENTARY FUNCTIONS, FIRST ORDER, FNLIB, TRIGONOMETRIC

AUTHOR
Fullerton, W., (LANL)

DESCRIPTION
Evaluate DATAN(X) from first order, that is, evaluate (DATAN(X)-X)/X**3 with relative error accuracy so that DATAN(X) = X + X**3*D9ATN1(X). Series for ATN1 on the interval 0. to 1.00000E+00 with weighted error 3.39E-32 log weighted error 31.47 significant figures required 30.26 decimal places required 32.27

REFERENCES
(NONE)

ROUTINES CALLED
D1MACH, DCSEVL, INITDS, XERMSG

REVISION HISTORY (YYMMDD)
780401 DATE WRITTEN
890531 Changed all specific intrinsics to generic. (WRB)
891115 Corrected third argument in reference to INITDS. (WRB)
891115 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)
900720 Routine changed from user-callable to subsidiary. (WRB)