- Unit Matrix / Identity Matrix
A diagonal matrix in which all the entries along the leading diagonal are equal to 1 is
said to be a unit matrix or identity matrix. Note that an identity matrix has to be
denoted only by the letter I. A unit matrix of order 2 is denoted as I 2 and a unit
matrix of order 3 is denoted as I 3.
Eg I = ⎟⎟
⎠
⎞
⎜⎜⎝
⎛
0 1
1 0
Here, the matrix I is an identity matrix of order 2 and hence it is denoted as I2.
The knowledge of the child with regard to the basic ideas of matrices, may facilitate
to understand the concept of unit matrix also, when the idea is narrated, supported
by necessary reading material in Braille.
- Negative of a Matrix
For a matrix A, its negative denoted as -A, is the matrix obtained by interchanging
the signs of the entries of the matrix A.
Eg. : If A = ⎟⎟
⎠
⎞
⎜⎜⎝
⎛
−
−
5 2 5
2 3 4
then,-A = ⎟⎟
⎠
⎞
⎜⎜⎝
⎛
− −
− −
5 2 5
2 3 4
The idea can be explained to the child through spatial presentation of the matrix.
- Addition of Matrices
Two matrices A and B can be added, only if they are of the same order. The resultant
matrix is obtained by adding the corresponding entries of the two matrices.
Eg. : Let A = ⎟⎟⎠
⎞
⎜⎜⎝
= ⎛
⎟⎟⎠
⎞
⎜⎜⎝
⎛
− 5 6
- 3 4
andB
3 4
1 2
