Dimensions of a Matrix

Dimensions of a matrix consists of rows and columns:

                          Matrix
                          [2 1]
                          [4 3]
Rows of a matrix go horizontally
                          Rows
                         [3 0 -7]
                         [-6 2 3]
Columns of a matrix go vertically
                      Columns
                       [2]
                                  [1]
                      [-9]

In order to find the dimension of a matrix you have to count the number of rows x columns:  

[ 3 1 6]: This is a 1x3 matrix because it has one row and 3 columns

[5  9]:This is a 2x2 matrix because there are two rows and 2 colmns 

[2 -4]


Identity Matrix:
 [0 1]: If you multiply the identity matrix with any other matrix
 [1 0]   then the product will be the non-identity matrix.

  [-3 1 ] x [0 1] =  [-3 1]
    [6   8]    [1  0]     [6 8]