code: private static double polyCosine(double x) {
          double x2 = x*x;
  
          double p = 2.479773539153719E-5;
          p = p * x2 + -0.0013888888689039883;
          p = p * x2 + 0.041666666666621166;
          p = p * x2 + -0.49999999999999994;
          p *= x2;
  
          return p;
      }
docs: Computes cos(x) - 1, where |x| < 1/16.
  Use a Remez polynomial approximation.
  @param x a number smaller than 1/16
  @return cos(x) - 1