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- *DECK CTAN
- COMPLEX FUNCTION CTAN (Z)
- C***BEGIN PROLOGUE CTAN
- C***PURPOSE Compute the complex tangent.
- C***LIBRARY SLATEC (FNLIB)
- C***CATEGORY C4A
- C***TYPE COMPLEX (CTAN-C)
- C***KEYWORDS ELEMENTARY FUNCTIONS, FNLIB, TANGENT, TRIGONOMETRIC
- C***AUTHOR Fullerton, W., (LANL)
- C***DESCRIPTION
- C
- C CTAN(Z) calculates the complex trigonometric tangent of complex
- C argument Z. Z is in units of radians.
- C
- C***REFERENCES (NONE)
- C***ROUTINES CALLED R1MACH, XERCLR, XERMSG
- C***REVISION HISTORY (YYMMDD)
- C 770401 DATE WRITTEN
- C 890531 Changed all specific intrinsics to generic. (WRB)
- C 890531 REVISION DATE from Version 3.2
- C 891214 Prologue converted to Version 4.0 format. (BAB)
- C 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
- C***END PROLOGUE CTAN
- COMPLEX Z
- SAVE SQEPS
- DATA SQEPS /0./
- C***FIRST EXECUTABLE STATEMENT CTAN
- IF (SQEPS.EQ.0.) SQEPS = SQRT (R1MACH(4))
- C
- X2 = 2.0*REAL(Z)
- Y2 = 2.0*AIMAG(Z)
- C
- SN2X = SIN (X2)
- CALL XERCLR
- C
- DEN = COS(X2) + COSH(Y2)
- IF (DEN .EQ. 0.) CALL XERMSG ('SLATEC', 'CTAN',
- + 'TAN IS SINGULAR FOR INPUT Z (X IS PI/2 OR 3*PI/2 AND Y IS 0)',
- + 2, 2)
- C
- IF (ABS(DEN).GT.MAX(ABS(X2),1.)*SQEPS) GO TO 10
- CALL XERCLR
- CALL XERMSG ('SLATEC', 'CTAN',
- + 'ANSWER LT HALF PRECISION, ABS(X) TOO BIG OR X TOO NEAR ' //
- + 'PI/2 OR 3*PI/2', 1, 1)
- C
- 10 CTAN = CMPLX (SN2X/DEN, SINH(Y2)/DEN)
- C
- RETURN
- END
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