 
      COMPLEX FUNCTION CATAN2(CSN,CCS)
C***BEGIN PROLOGUE  CATAN2
C***DATE WRITTEN   770401   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  C4A
C***KEYWORDS  ARC TANGENT,COMPLEX,ELEMENTARY FUNCTION,QUADRANT
C***AUTHOR  FULLERTON, W., (LANL)
C***PURPOSE  Computes the complex arc Tangent in the proper quadrant.
C***DESCRIPTION
C
C CATAN2(CSN,CCS) calculates the complex trigonometric arc
C tangent of the ratio CSN/CCS and returns a result whose real
C part is in the correct quadrant (within a multiple of 2*PI).  The
C result is in units of radians and the real part is between -PI
C and +PI.
C***REFERENCES  (NONE)
C***ROUTINES CALLED  CATAN,XERROR
C***END PROLOGUE  CATAN2
 
 
