Example: How to Find Area of a Circle with Diameter in C# using Math.PI Constant

C
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// How to Find Area of a Circle with Diameter in C# using Math.PI Constant
using System;

public class W3CW {
    static public void Main (string[] args) {
        Console.WriteLine("Enter the radius of the circle::\n");
        float r=Convert.ToInt32(Console.ReadLine());
        double d, c, a;
        
        // It will calculate the diameter, circumference, and area
        d = 2 * r;
        c = 2 * Math.PI * r;
        a = Math.PI * (r * r);
        
        // It will print the final output
        Console.WriteLine("Diameter      = "+d+" units");
        Console.WriteLine("Circumference = "+c+" units");
        Console.WriteLine("Area          = "+a+" sq. units");
    }
}