Identity and Inverse Matrix

Taught Identity and Inverse Matrix for my 5 KA class today. Glad to see most of them are able to find the inverse of a 2 x 2 matrix. Sadly there are some girls who are not interested at all in learning. It's not easy being a teacher, having to deal with all sorts of students. There are those who are very bright and self motivated. I don't have to worry about them. Then there's those who are slower but willing to learn. I enjoy being able to help them. Then there are those who's not interested at all, that's where my headache is. How to make them interested in learning???? Any ideas?? Sometimes I do wonder what they think about when they're in school. The sad thing is I know that they're capable of better things but they're are not willing to try. Enough of my ramblings, I'm suppose to write on the lesson that I did today :

Identity Matrix (I)

A square matrix in which all the main diagonal elements are 1’s and all the remaining elements are 0’s is called an Identity Matrix.

# Identity Matrix is denoted with the letter “In×n”, where n×n represents the order of the matrix.
# One of the important properties of identity matrix is: A×In×n = A, where A is any square matrix of order n×n.

Example
2 x 2 Identity Matrix


3 x 3 Identity matrix



n x n Identity matrix



Inverse Matrix
For a square matrix A, the inverse is written A-1. When A is multiplied by A-1 the result is the identity matrix, I.

AA-1 = A-1A = I
Example: For matrix A = ,


its inverse is


since AA-1 =


and A-1A =

Please do all the assignment given so that we can discuss the answers next week.