github.com/afumu/libc@v0.0.6/musl/src/math/__cosdf.c (about)

     1  /* origin: FreeBSD /usr/src/lib/msun/src/k_cosf.c */
     2  /*
     3   * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
     4   * Debugged and optimized by Bruce D. Evans.
     5   */
     6  /*
     7   * ====================================================
     8   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
     9   *
    10   * Developed at SunPro, a Sun Microsystems, Inc. business.
    11   * Permission to use, copy, modify, and distribute this
    12   * software is freely granted, provided that this notice
    13   * is preserved.
    14   * ====================================================
    15   */
    16  
    17  #include "libm.h"
    18  
    19  /* |cos(x) - c(x)| < 2**-34.1 (~[-5.37e-11, 5.295e-11]). */
    20  static const double
    21  C0  = -0x1ffffffd0c5e81.0p-54, /* -0.499999997251031003120 */
    22  C1  =  0x155553e1053a42.0p-57, /*  0.0416666233237390631894 */
    23  C2  = -0x16c087e80f1e27.0p-62, /* -0.00138867637746099294692 */
    24  C3  =  0x199342e0ee5069.0p-68; /*  0.0000243904487962774090654 */
    25  
    26  float __cosdf(double x)
    27  {
    28  	double_t r, w, z;
    29  
    30  	/* Try to optimize for parallel evaluation as in __tandf.c. */
    31  	z = x*x;
    32  	w = z*z;
    33  	r = C2+z*C3;
    34  	return ((1.0+z*C0) + w*C1) + (w*z)*r;
    35  }