C# 数学函数

和其他程序员一样，我也是编程世界的新手，我想生活在这个世界上，并在你的帮助下获得回报。所以，我必须在 Cmath 中使用数学函数。

函数是

z1 = Sin2α + sin5α - Sin3α / cosα+1-2sin^2(2α)
z2= √x^3 + 3 / x^3 - 3

到目前为止我的结果...

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine ("First Program");
            Console.WriteLine ("Enter an integer");
            int x;
            x = int.Parse(Console.ReadLine());
            Console.WriteLine ("x = " + x);
            Console.WriteLine("Enter a valid number");

            //Solving the functions
            double a = double.Parse(Console.ReadLine()); //Read the angle in degrees
            a = a / 180 * Math.PI;
            double z = (Math.Cos(a)) + (Math.Cos(2 * a)) + (Math.Sin(6 * a)) + (Math.Cos(7 * a));
            z = (x * x) + (2(x)) - (3) + (x + 1) * Math.Sqrt(x * x - 9) / (x * x) - (2(x)) - (3) + (x - 1) * Math.Sqrt(x * x - 9);


            Console.WriteLine(z);

double z1(double alpha)
{
    return Math.Sin(2.0f * alpha)
         + Math.Sin(5.0f * alpha)
         - Math.Sin(3.0f * alpha) / Math.Cos(alpha)
                                    + 1.0f + 2.0f * Math.Sin(2.0f * alpha);
}
double z2(double x)
{
    return Math.Sqrt(x * x * x) + 3.0f / (x * x * x) - 3.0f;
}