code: public static double Highprecision_Exp(double x) {
          return (362880 + x * (362880 + x * (181440 + x * (60480 + x * (15120 + x * (3024 + x * (504 + x * (72 + x * (9 + x))))))))) * 2.75573192e-6;
      }
docs: Calculate Exp.
  Exp by Taylor series (9).
  
  @param x Value.
  @return Exponential.