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

     1  /* origin: FreeBSD /usr/src/lib/msun/src/k_sinf.c */
     2  /*
     3   * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
     4   * 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  /* |sin(x)/x - s(x)| < 2**-37.5 (~[-4.89e-12, 4.824e-12]). */
    20  static const double
    21  S1 = -0x15555554cbac77.0p-55, /* -0.166666666416265235595 */
    22  S2 =  0x111110896efbb2.0p-59, /*  0.0083333293858894631756 */
    23  S3 = -0x1a00f9e2cae774.0p-65, /* -0.000198393348360966317347 */
    24  S4 =  0x16cd878c3b46a7.0p-71; /*  0.0000027183114939898219064 */
    25  
    26  float __sindf(double x)
    27  {
    28  	double_t r, s, w, z;
    29  
    30  	/* Try to optimize for parallel evaluation as in __tandf.c. */
    31  	z = x*x;
    32  	w = z*z;
    33  	r = S3 + z*S4;
    34  	s = z*x;
    35  	return (x + s*(S1 + z*S2)) + s*w*r;
    36  }