Program:

The source code to print the lower triangular matrix is given below. The given program is compiled and executed successfully on Microsoft Visual Studio.

//C# program to print lower triangular matrix.

using System;

class MatrixDemo
{
    public static void Main(string[] args)
    {
        int i   = 0;
        int j   = 0;

        int row = 3;
        int col = 3;

        int[,] Matrix = new int[row, col];
        
        Console.Write("Enter the elements of matrix: ");
        for (i = 0; i < row; i++)
        {
            for (j = 0; j < col; j++)
            {
                Matrix[i, j] = int.Parse(Console.ReadLine());
            }
        }

        Console.WriteLine("\nMatrix");
        for (i = 0; i < row; i++)
        {
            for (j = 0; j < col; j++)
            {
                Console.Write(Matrix[i, j] + "\t");
            }
            Console.WriteLine();
        }

        Console.WriteLine("Lower triangular matrix: ");
        for (i = 0; i < row; i++)
        {
            Console.WriteLine();
            for (j = 0; j < col; j++)
            {
                if (i >= j)
                    Console.Write(Matrix[i, j] + "\t");
                else
                    Console.Write(" \t");
            }
        }

        Console.WriteLine();
    }
}

Output:

Enter the elements of matrix: 1
2
3
4
5
5
6
7
8

Matrix
1       2       3
4       5       5
6       7       8
Lower triangular matrix:

1
4       5
6       7       8
Press any key to continue . . .

Explanation:

In the above program, we created a class MatrixDemo that contains the Main() method. Here, we read a 3X3 matrix and then print the lower triangular matrix on the console screen using the below code.

for (i = 0; i < row; i++)
{
    Console.WriteLine();
    for (j = 0; j < col; j++)
    {
        if (i >= j)
            Console.Write(Matrix[i, j] + "\t");
        else
            Console.Write(" \t");
    }
}