11 Matrices

The transpose of a matrix is when the rows and columns are interchanged:    kjjk aa  T, AA The diagonal elements of a square matrix are called the principal or main diagonal and the sum of these is called the trace of the matrix. A square matrix in which the main diagonal elements are all 1 and all other elements are 0 is called a unit matrix. For a square matrix A, if there exists a matrix B such that AB = I, then B is the inverse of A and I written B1. Not every square matrix has an inverse.