18 Matrix SingularityIf the inverse of a matrix A exists, then A is said to be nonsingular.If the inverse of a matrix A does not exist, then A is said to be singular.If matrix A is singular, then the linear system of simultaneous equations represented by A has no unique solution.
19 There are an infinite number of solutions if 2a = b. There is no feasible solution if 2a b.Thus matrix A is singular.
20 trace of a square matrix = sum of diagonal elements matrix augmentation: addition of a column or columnsto the initial matrix
22 VectorsColumn vectorRow vectorVectors of two ordinates
23 orthogonal vectorsTwo vectors are said to be orthogonal if their product is equal to zero.If two vector are orthogonal, they are perpendicular to each other in the n-dimensional space.
24 normalized vectorsA vector is normalized by dividing each element by its length.A normalized vector has a length 1.Two vectors that are both normalized and orthogonal to each other are said to be orthonormal vectors.
27 Determinants A determinant of a matrix A is denoted by |A|. The determinant of a 22 matrix:The determinant of a 33 matrix:
28 The determinant of an nn matrix: The minor of aij, denoted by Aij, is the matrix after removing row i and column j.The determinant of an nn matrix:The general expression for the determinant of an nn matrix:
29 Example: Matrix Determinant with the first row and their minors:
30 with the second column and their minors: Since |A|=0, A is a singular matrix; that is the inverse of A doest not exist.
31 Properties of Determinants 1. If the values in any row (column) are proportional to the corresponding values in another row(column), the determinant equals zero
32 2. If all the elements in any row(column) equal zero, the determinant equals zero. 3. If all the elements of any row(column) are multiplied by a constant c, the value of the determinant is multiplied by c.
33 4. The value of the determinant is not changed by adding any row (column) multiplied by a constant c to another row (column).5. If any two rows (columns) are interchanged, the sign of the determinant is changed.
34 6. The determinant of a matrix equals that of its transpose; that is, |A| = |AT|. 7. If a matrix A is placed in diagonal form, then the product of the elements on the diagonal equals the determinant of A.
35 8. If a matrix A has a zero determinant, then A is a singular matrix; that is, the inverse of A does not exist.
36 Rank of A MatrixA matrix of r rows and c columns is said to be of order r by c. If it is a square matrix, r by r, then the matrix is of order r.The rank of a matrix equals the order of highest-order nonsingular submatrix.
37 Example 1: Rank of Matrix 3 square submatrices:Each of these has a determinant of 0, so the rank is less than 2. Thus the rank of R is 1.
38 Example 2: Rank of Matrix Since |A|=0, the rank is not 3. The following submatrix has a nonzero determinant:Thus, the rank of A is 2.