Program:

The source code to calculate the Cosine(X) using the predefined method is given below. The given program is compiled and executed successfully on Microsoft Visual Studio.

//C# program to calculate the Cos(X) 
//using the predefined method. 

using System;

class Demo
{
    
    static void Main(string[] args)
    {
        double val = 0.0F;

        while(val<=5)
        {
            Console.WriteLine("Cos({0}) => {1}", val, Math.Cos(val));
            val++;
        }
        Console.WriteLine();
    }
}

Output:

Cos(0) => 1
Cos(1) => 0.54030230586814
Cos(2) => -0.416146836547142
Cos(3) => -0.989992496600445
Cos(4) => -0.653643620863612
Cos(5) => 0.283662185463226

Press any key to continue . . .

Explanation:

Here, we created a class Demo that contains the Main() method, the Main() is the entry point of the program, here we calculated the Cosine(X) using the predefined method Cos() of Math class. Here we calculated Cosine(X) for values 0 to 5 and print the results on the console screen.