Definition of Determinant of Matrix
Determinant of a Matrix is defined as the sum of products of the elements of any row or column along with their corresponding co-factors. Determinant is defined only for square matrices.
Determinant of any square matrix of order 2×2, 3×3, 4×4, or n × n, where n is the number of rows or the number of columns. (For a square matrix number of rows and columns are equal). Determinant can also be defined as the function which maps every matrix with the real numbers.
For any set S of all square matrices, and R the set of all numbers the function f, f: S → R is defined as f (x) = y, where x ∈ S and y ∈ R, then f (x) is called the determinant of the input matrix.
Symbol of Determinant
Let’s take any square matrix A, then the determinant of A is denoted as det A (or) |A|. Determinant is also denoted by the symbol Δ.
Minor of Element of Matrix
Minor is required to find determinant for single elements (every element) of the matrix. They are the determinants for every element obtained by eliminating the rows and columns of that element. If the matrix given is:
[Tex]\begin{bmatrix}a_{11} & a_{12} &a_{13}\\a_{21} & a_{22} & a_{23}\\a_{31} & a_{32} & a_{33}\end{bmatrix}[/Tex]
Minor of a12 will be the determinant:
[Tex]\begin{vmatrix}a_{21} & a_{23}\\a_{31} & a_{33}\end{vmatrix}[/Tex]
Question: Find the Minor of element 5 in the determinant [Tex]\begin{vmatrix}2 & 1 & 2\\4 & 5 & 0\\2 & 0 & 1\end{vmatrix}[/Tex]
Answer:
The minor of element 5 will be the determinant of [Tex]\begin{vmatrix}2 & 2\\2 & 1\end{vmatrix}[/Tex]
Calculating the determinant, the minor is obtained as:
(2 × 1) – (2 × 2) = -2
Cofactors of Element of Matrix
Cofactors are related to minors by a small formula, for an element aij, the cofactor of this element is Cij and the minor is Mij then, the cofactor can be written as:
Cij = (-1)i+jMij
Question: Find the cofactor of the element placed in the first row and second column of the determinant:
[Tex]\begin{vmatrix}2 & 1 & 2\\4 & 5 & 0\\2 & 0 & 1\end{vmatrix}[/Tex]
Answer:
In order to find out the cofactor of the first row and second column element i.e the cofactor for 1. First find out the minor for 1, which will be:
[Tex]\begin{vmatrix}4 & 0\\2 & 1\end{vmatrix} \\ = (4 \times 1) – (2 \times 0) \\ = 4[/Tex]
M12 = 4
Now, applying the formula for cofactor:
C12 = (-1)1 + 2M12
C12 = (-1)3 × 4
C12 = -4
Adjoint of a Matrix
The Adjoint of a matrix for order n can be defined as the transpose of its cofactors. For a matrix A:
Adj. A = [Cij]n×nT
Transpose of a Matrix
Transpose of a Matrix A is denoted as AT or A’. It is clear that the vertical side in the matrix is known as a column and the horizontal side is known as a row, Transposing a Matrix means replacing the Rows with columns and Vice-Versa, since the Rows and Columns are changing, the Order of the Matrix also changes.
If a Matrix is given as A= [aij]m×n, then its Transpose will become
AT or A’ = [aji]n×m
Question: What will be the transpose of the Matrix A =
[Tex]\begin{bmatrix}2 & 1\\3 & 0\\6 & 9\end{bmatrix}_{2\times3}[/Tex]
Answer:
Interchanging Rows and Columns, AT = [Tex]\begin{bmatrix}2 & 3 & 6\\1 & 0 & 9\end{bmatrix}_{3\times2}[/Tex]
Determinant of a Matrix with Solved Examples
Determinant of a Matrix is defined as the function that gives the unique output (real number) for every input value of the matrix. Determinant of the matrix is considered the scaling factor that is used for the transformation of a matrix. It is useful for finding the solution of a system of linear equations, the inverse of the square matrix, and others. The determinant of only square matrices exists.
Table of Content
- Determinant of Matrix Calculator
- Definition of Determinant of Matrix
- Determinant of a 1×1 Matrix
- Determinant of 2×2 Matrix
- Determinant of a 3×3 Matrix
- Determinant of 4×4 Matrix
- Determinant of Identity Matrix
- Determinant of Symmetric Matrix
- Determinant of Skew-Symmetric Matrix
- Determinant of Inverse Matrix
- Determinant of Orthogonal Matrix
- Physical Significance of Determinant
- Laplace Formula for Determinant
- Properties of Determinants of Matrix