      COMPLEX FUNCTION CTAN(Z)
C***BEGIN PROLOGUE  CTAN
C***DATE WRITTEN   770401   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  C4A
C***KEYWORDS  COMPLEX,ELEMENTARY FUNCTION,TANGENT
C***AUTHOR  FULLERTON, W., (LANL)
C***PURPOSE  Computes the complex Tangent.
C***DESCRIPTION
C
C CTAN(Z) calculates the complex trigonometric tangent of complex
C argument Z.  Z is in units of radians.
C***REFERENCES  (NONE)
C***ROUTINES CALLED  R1MACH,XERCLR,XERROR
C***END PROLOGUE  CTAN
