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37 lines
1.2 KiB
Fortran
37 lines
1.2 KiB
Fortran
*DECK DCOSDG
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DOUBLE PRECISION FUNCTION DCOSDG (X)
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C***BEGIN PROLOGUE DCOSDG
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C***PURPOSE Compute the cosine of an argument in degrees.
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C***LIBRARY SLATEC (FNLIB)
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C***CATEGORY C4A
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C***TYPE DOUBLE PRECISION (COSDG-S, DCOSDG-D)
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C***KEYWORDS COSINE, DEGREES, ELEMENTARY FUNCTIONS, FNLIB,
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C TRIGONOMETRIC
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C***AUTHOR Fullerton, W., (LANL)
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C***DESCRIPTION
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C
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C DCOSDG(X) calculates the double precision trigonometric cosine
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C for double precision argument X in units of degrees.
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C
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C***REFERENCES (NONE)
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C***ROUTINES CALLED (NONE)
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C***REVISION HISTORY (YYMMDD)
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C 770601 DATE WRITTEN
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C 890531 Changed all specific intrinsics to generic. (WRB)
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C 890531 REVISION DATE from Version 3.2
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C 891214 Prologue converted to Version 4.0 format. (BAB)
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C***END PROLOGUE DCOSDG
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DOUBLE PRECISION X, RADDEG
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SAVE RADDEG
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DATA RADDEG / 0.0174532925 1994329576 9236907684 886 D0 /
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C***FIRST EXECUTABLE STATEMENT DCOSDG
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DCOSDG = COS (RADDEG*X)
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C
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IF (MOD(X,90.D0).NE.0.D0) RETURN
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N = ABS(X)/90.D0 + 0.5D0
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N = MOD (N, 2)
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IF (N.EQ.0) DCOSDG = SIGN (1.0D0, DCOSDG)
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IF (N.EQ.1) DCOSDG = 0.0D0
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C
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RETURN
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END
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