double N(double x) { return(0.5 * (1.0 + SpecialFunction.erf(x / Math.Sqrt(2.0)))); }
public double concX() { return(Math.Round((((1 - ((SpecialFunction.erf((((x / (2 * Math.Sqrt((d0 * Math.Exp(-qd / (r * (temp + 273.15)))) * time))))))))) * (cs - c0)) + c0), 5)); }