Identity matrix
From Conservapedia
In mathematics the identity matrix is the matrix which, when multiplying, does not change the size or values of the matrix by which it is multiplied. The identity matrix is usually denoted 
or 
, and the operation of multiplication is described as,
or 
The identity matrix is an 
matrix where the leading diagonal is ones and all other entries are zero. That is, 
, and 
whenever 
.
