1*DECK DFDEQC
2      SUBROUTINE DFDEQC (T, U, UPRIME, RPAR, IPAR)
3C***BEGIN PROLOGUE  DFDEQC
4C***SUBSIDIARY
5C***PURPOSE  Derivative evaluator for DDEPAC quick checks.
6C***LIBRARY   SLATEC
7C***TYPE      DOUBLE PRECISION (FDEQC-S, DFDEQC-D)
8C***AUTHOR  Chow, Jeff, (LANL)
9C***ROUTINES CALLED  (NONE)
10C***REVISION HISTORY  (YYMMDD)
11C   810801  DATE WRITTEN
12C   891214  Prologue converted to Version 4.0 format.  (BAB)
13C   900415  Name changed from DDF to DFDEQC.  (WRB)
14C***END PROLOGUE  DFDEQC
15C
16C     Declare arguments.
17C
18      INTEGER IPAR(*)
19      DOUBLE PRECISION RPAR(*), T, U(*), UPRIME(*)
20C
21C     Declare local variables.
22C
23      DOUBLE PRECISION R, RSQ, R3
24C***FIRST EXECUTABLE STATEMENT  DFDEQC
25      RSQ = U(1)*U(1) + U(2)*U(2)
26      R = SQRT(RSQ)
27      R3 = RSQ*R
28      UPRIME(1) = U(3)
29      UPRIME(2) = U(4)
30      UPRIME(3) = -(U(1)/R3)
31      UPRIME(4) = -(U(2)/R3)
32      RETURN
33      END
34