using System;

using org.matheval;

public class Program

{

    public static void Main()

    {

        Expression expr = new Expression("tan(a)^3-((3*sin(a)-sin(3*a))/(3*cos(a)+cos(3*a)))");

        expr.Bind("a", System.Math.PI / 4);

        Console.WriteLine(expr.Eval<Decimal>());

    }

}