Definition 3:The matrix composed of one line, is called as a matrix-line and is designated so . And from one column - by a matrix-column and is designated so .
Definition 4:The matrix is called square n-th order, if number of its lines equals number of columns and equals n.
Example of a square matrix of the third order:
Definition 5:Elements of a square matrix at which number of a column is equal to number of a line are called as diagonal elements and make the main diagonal of a matrix.
Definition 6:If all not diagonal elements of a square matrix are equal to zero, in that case the matrix is called as a diagonal matrix.
It has the following form:
Definition 7:If at a diagonal matrix of n-th order all diagonal elements are equal to 1 (unity) then the matrix is called as an unit matrix of n-th order and is designated by letter Е.
It has the following form:
Definition 8:The matrix of any dimension is called zero if all its elements are equal to zero and is designated by letter O.