42 lines
772 B
C
42 lines
772 B
C
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/* ctan.c */
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/*
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Contributed by Danny Smith
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2003-10-20
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*/
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#include <math.h>
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#include <complex.h>
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#include <errno.h>
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/* ctan (x + I * y) = (sin (2 * x) + I * sinh(2 * y))
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/ (cos (2 * x) + cosh (2 * y)) */
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double complex ctan (double complex Z)
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{
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double complex Res;
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double two_I = 2.0 * __imag__ Z;
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double two_R = 2.0 * __real__ Z;
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double denom = cos (two_R) + cosh (two_I);
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if (denom == 0.0)
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{
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errno = ERANGE;
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__real__ Res = HUGE_VAL;
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__imag__ Res = HUGE_VAL;
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}
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else if (isinf (denom))
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{
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errno = ERANGE;
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__real__ Res = 0.0;
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__imag__ Res = two_I > 0 ? 1.0 : -1.0;
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}
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else
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{
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__real__ Res = sin (two_R) / denom;
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__imag__ Res = sinh (two_I) / denom;
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}
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return Res;
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}
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