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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.17.0/] [newlib/] [libm/] [mathfp/] [s_tan.c] - Rev 148
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/* @(#)z_tan.c 1.0 98/08/13 */ /****************************************************************** * The following routines are coded directly from the algorithms * and coefficients given in "Software Manual for the Elementary * Functions" by William J. Cody, Jr. and William Waite, Prentice * Hall, 1980. ******************************************************************/ /* FUNCTION <<tan>>, <<tanf>>---tangent INDEX tan INDEX tanf ANSI_SYNOPSIS #include <math.h> double tan(double <[x]>); float tanf(float <[x]>); TRAD_SYNOPSIS #include <math.h> double tan(<[x]>) double <[x]>; float tanf(<[x]>) float <[x]>; DESCRIPTION <<tan>> computes the tangent of the argument <[x]>. Angles are specified in radians. <<tanf>> is identical, save that it takes and returns <<float>> values. RETURNS The tangent of <[x]> is returned. PORTABILITY <<tan>> is ANSI. <<tanf>> is an extension. */ /****************************************************************** * Tangent * * Input: * x - floating point value * * Output: * tangent of x * * Description: * This routine calculates the tangent of x. * *****************************************************************/ #include "fdlibm.h" #include "zmath.h" #ifndef _DOUBLE_IS_32BITS static const double TWO_OVER_PI = 0.63661977236758134308; static const double p[] = { -0.13338350006421960681, 0.34248878235890589960e-2, -0.17861707342254426711e-4 }; static const double q[] = { -0.46671683339755294240, 0.25663832289440112864e-1, -0.31181531907010027307e-3, 0.49819433993786512270e-6 }; double _DEFUN (tan, (double), double x) { double y, f, g, XN, xnum, xden, res; int N; /* Check for special values. */ switch (numtest (x)) { case NAN: errno = EDOM; return (x); case INF: errno = EDOM; return (z_notanum.d); } y = fabs (x); /* Check for values that are out of our range. */ if (y > 105414357.0) { errno = ERANGE; return (y); } if (x < 0.0) N = (int) (x * TWO_OVER_PI - 0.5); else N = (int) (x * TWO_OVER_PI + 0.5); XN = (double) N; f = x - N * __PI_OVER_TWO; /* Check for values that are too small. */ if (-z_rooteps < f && f < z_rooteps) { xnum = f; xden = 1.0; } /* Calculate the polynomial. */ else { g = f * f; xnum = f * ((p[2] * g + p[1]) * g + p[0]) * g + f; xden = (((q[3] * g + q[2]) * g + q[1]) * g + q[0]) * g + 1.0; } if (N & 1) { xnum = -xnum; res = xden / xnum; } else { res = xnum / xden; } return (res); } #endif /* _DOUBLE_IS_32BITS */
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