Page 1
LINEAR ALGEBRA
MATRICES
A matrix is a rectangular array of numbers (or functions) enclosed in brackets. These numbers
(or function) are called entries of elements of the matrix.
Example:
??
??
??
2 0.4 8
5 -32 0
order = 2 x 3, 2 = no. of rows, 3 = no. of columns
Special Type of Matrices
1. Square Matrix
A m x n matrix is called as a square matrix if m = n i.e, no of rows = no. of columns
The elements
ij
a when i = j
? ?
11 22
a a ......... are called diagonal elements
Example:
??
??
??
12
45
2. Diagonal Matrix
A square matrix in which all non-diagonal elements are zero and diagonal elements may or
may not be zero.
Example:
??
??
??
10
05
Properties
a. diag [x, y, z] + diag [p, q, r] = diag [x + p, y + q, z + r]
b. diag [x, y, z] × diag [p, q, r] = diag [xp, yq, zr]
c.
? ?
?
??
?? ?
?? ??
??
1
1 1 1
diag x, y, z diag , ,
x y z
d.
? ?
??
??
t
diag x, y, z = diag [x, y, z]
e.
? ?
?? ?? ?
?? ??
n
n n n
diag x, y, z diag x ,y ,z
f. Eigen value of diag [x, y, z] = x, y & z
g. Determinant of diag [x, y, z] = xyz
3. Scalar Matrix
A diagonal matrix in which all diagonal elements are equal.
Page 2
LINEAR ALGEBRA
MATRICES
A matrix is a rectangular array of numbers (or functions) enclosed in brackets. These numbers
(or function) are called entries of elements of the matrix.
Example:
??
??
??
2 0.4 8
5 -32 0
order = 2 x 3, 2 = no. of rows, 3 = no. of columns
Special Type of Matrices
1. Square Matrix
A m x n matrix is called as a square matrix if m = n i.e, no of rows = no. of columns
The elements
ij
a when i = j
? ?
11 22
a a ......... are called diagonal elements
Example:
??
??
??
12
45
2. Diagonal Matrix
A square matrix in which all non-diagonal elements are zero and diagonal elements may or
may not be zero.
Example:
??
??
??
10
05
Properties
a. diag [x, y, z] + diag [p, q, r] = diag [x + p, y + q, z + r]
b. diag [x, y, z] × diag [p, q, r] = diag [xp, yq, zr]
c.
? ?
?
??
?? ?
?? ??
??
1
1 1 1
diag x, y, z diag , ,
x y z
d.
? ?
??
??
t
diag x, y, z = diag [x, y, z]
e.
? ?
?? ?? ?
?? ??
n
n n n
diag x, y, z diag x ,y ,z
f. Eigen value of diag [x, y, z] = x, y & z
g. Determinant of diag [x, y, z] = xyz
3. Scalar Matrix
A diagonal matrix in which all diagonal elements are equal.
4. Identity Matrix
A diagonal matrix whose all diagonal elements are 1. Denoted by I
Properties
a. AI = IA = A
b.
?
n
II
c.
?
?
1
II
d. det(I) = 1
5. Null matrix
An m x n matrix whose all elements are zero. Denoted by O.
Properties:
a. A + O = O + A = A
b. A + (- A) = O
6. Upper Triangular Matrix
A square matrix whose lower off diagonal elements are zero.
Example:
??
??
??
??
??
3 4 5
0 6 7
0 0 9
7. Lower Triangular Matrix
A square matrix whose upper off diagonal elements are zero.
Example:
??
??
??
??
??
3 0 0
4 6 0
5 7 9
8. Idempotent Matrix
A matrix is called Idempotent if ?
2
AA
Example:
??
??
??
10
01
9. Involutary Matrix
A matrix is called Involutary if ?
2
AI .
Page 3
LINEAR ALGEBRA
MATRICES
A matrix is a rectangular array of numbers (or functions) enclosed in brackets. These numbers
(or function) are called entries of elements of the matrix.
Example:
??
??
??
2 0.4 8
5 -32 0
order = 2 x 3, 2 = no. of rows, 3 = no. of columns
Special Type of Matrices
1. Square Matrix
A m x n matrix is called as a square matrix if m = n i.e, no of rows = no. of columns
The elements
ij
a when i = j
? ?
11 22
a a ......... are called diagonal elements
Example:
??
??
??
12
45
2. Diagonal Matrix
A square matrix in which all non-diagonal elements are zero and diagonal elements may or
may not be zero.
Example:
??
??
??
10
05
Properties
a. diag [x, y, z] + diag [p, q, r] = diag [x + p, y + q, z + r]
b. diag [x, y, z] × diag [p, q, r] = diag [xp, yq, zr]
c.
? ?
?
??
?? ?
?? ??
??
1
1 1 1
diag x, y, z diag , ,
x y z
d.
? ?
??
??
t
diag x, y, z = diag [x, y, z]
e.
? ?
?? ?? ?
?? ??
n
n n n
diag x, y, z diag x ,y ,z
f. Eigen value of diag [x, y, z] = x, y & z
g. Determinant of diag [x, y, z] = xyz
3. Scalar Matrix
A diagonal matrix in which all diagonal elements are equal.
4. Identity Matrix
A diagonal matrix whose all diagonal elements are 1. Denoted by I
Properties
a. AI = IA = A
b.
?
n
II
c.
?
?
1
II
d. det(I) = 1
5. Null matrix
An m x n matrix whose all elements are zero. Denoted by O.
Properties:
a. A + O = O + A = A
b. A + (- A) = O
6. Upper Triangular Matrix
A square matrix whose lower off diagonal elements are zero.
Example:
??
??
??
??
??
3 4 5
0 6 7
0 0 9
7. Lower Triangular Matrix
A square matrix whose upper off diagonal elements are zero.
Example:
??
??
??
??
??
3 0 0
4 6 0
5 7 9
8. Idempotent Matrix
A matrix is called Idempotent if ?
2
AA
Example:
??
??
??
10
01
9. Involutary Matrix
A matrix is called Involutary if ?
2
AI .
Matrix Equality
Two matrices ? ?
? mn
A and ? ?
? p q
B are equal if
m = p ; n = q i.e., both have same size
ij
a =
ij
b for all values of i & j.
Addition of Matrices
For addition to be performed, the size of both matrices should be same.
If [C] = [A] + [B]
Then ??
ij ij ij
c a b
i.e., elements in same position in the two matrices are added.
Subtraction of Matrices
[C] = [A] – [B]
= [A] + [–B]
Difference is obtained by subtraction of all elements of B from elements of A.
Hence here also, same size matrices should be there.
Scalar Multiplication
The product of any m × n matrix A
??
??
??
jk
a and any scalar c, written as cA, is the m × n
matrix cA =
??
??
??
jk
ca obtained by multiplying each entry in A by c.
Multiplication of two matrices
Let ? ?
? m n
A and ? ?
? p q
B be two matrices and C = AB, then for multiplication, [n = p]
should hold. Then,
?
?
?
n
jk
j1
ik ij
C a b
Properties
? If AB exists then BA does not necessarily exists.
Example: ? ?
? 3 4
A , ? ?
? 4 5
B , then AB exits but BA does not exists as 5 ? 3
So, matrix multiplication is not commutative.
Page 4
LINEAR ALGEBRA
MATRICES
A matrix is a rectangular array of numbers (or functions) enclosed in brackets. These numbers
(or function) are called entries of elements of the matrix.
Example:
??
??
??
2 0.4 8
5 -32 0
order = 2 x 3, 2 = no. of rows, 3 = no. of columns
Special Type of Matrices
1. Square Matrix
A m x n matrix is called as a square matrix if m = n i.e, no of rows = no. of columns
The elements
ij
a when i = j
? ?
11 22
a a ......... are called diagonal elements
Example:
??
??
??
12
45
2. Diagonal Matrix
A square matrix in which all non-diagonal elements are zero and diagonal elements may or
may not be zero.
Example:
??
??
??
10
05
Properties
a. diag [x, y, z] + diag [p, q, r] = diag [x + p, y + q, z + r]
b. diag [x, y, z] × diag [p, q, r] = diag [xp, yq, zr]
c.
? ?
?
??
?? ?
?? ??
??
1
1 1 1
diag x, y, z diag , ,
x y z
d.
? ?
??
??
t
diag x, y, z = diag [x, y, z]
e.
? ?
?? ?? ?
?? ??
n
n n n
diag x, y, z diag x ,y ,z
f. Eigen value of diag [x, y, z] = x, y & z
g. Determinant of diag [x, y, z] = xyz
3. Scalar Matrix
A diagonal matrix in which all diagonal elements are equal.
4. Identity Matrix
A diagonal matrix whose all diagonal elements are 1. Denoted by I
Properties
a. AI = IA = A
b.
?
n
II
c.
?
?
1
II
d. det(I) = 1
5. Null matrix
An m x n matrix whose all elements are zero. Denoted by O.
Properties:
a. A + O = O + A = A
b. A + (- A) = O
6. Upper Triangular Matrix
A square matrix whose lower off diagonal elements are zero.
Example:
??
??
??
??
??
3 4 5
0 6 7
0 0 9
7. Lower Triangular Matrix
A square matrix whose upper off diagonal elements are zero.
Example:
??
??
??
??
??
3 0 0
4 6 0
5 7 9
8. Idempotent Matrix
A matrix is called Idempotent if ?
2
AA
Example:
??
??
??
10
01
9. Involutary Matrix
A matrix is called Involutary if ?
2
AI .
Matrix Equality
Two matrices ? ?
? mn
A and ? ?
? p q
B are equal if
m = p ; n = q i.e., both have same size
ij
a =
ij
b for all values of i & j.
Addition of Matrices
For addition to be performed, the size of both matrices should be same.
If [C] = [A] + [B]
Then ??
ij ij ij
c a b
i.e., elements in same position in the two matrices are added.
Subtraction of Matrices
[C] = [A] – [B]
= [A] + [–B]
Difference is obtained by subtraction of all elements of B from elements of A.
Hence here also, same size matrices should be there.
Scalar Multiplication
The product of any m × n matrix A
??
??
??
jk
a and any scalar c, written as cA, is the m × n
matrix cA =
??
??
??
jk
ca obtained by multiplying each entry in A by c.
Multiplication of two matrices
Let ? ?
? m n
A and ? ?
? p q
B be two matrices and C = AB, then for multiplication, [n = p]
should hold. Then,
?
?
?
n
jk
j1
ik ij
C a b
Properties
? If AB exists then BA does not necessarily exists.
Example: ? ?
? 3 4
A , ? ?
? 4 5
B , then AB exits but BA does not exists as 5 ? 3
So, matrix multiplication is not commutative.
? Matrix multiplication is not associative.
A(BC) ? (AB)C .
? Matrix Multiplication is distributive with respect to matrix addition
A(B + C) = AB +AC
? If AB = AC ? B = C (if A is non-singular)
BA = CA ? B = C (if A is non-singular)
Transpose of a matrix
If we interchange the rows by columns of a matrix and vice versa we obtain transpose of a
matrix.
eg., A =
??
??
??
??
??
13
24
65
;
??
?
??
??
T
126
A
3 4 5
Conjugate of a matrix
The matrix obtained by replacing each element of matrix by its complex conjugate.
Properties
a.
? ?
? AA
b.
? ?
? ? ? A B A B
c.
? ?
? KA K A
d.
? ?
? AB AB
Transposed conjugate of a matrix
The transpose of conjugate of a matrix is called transposed conjugate. It is represented by
?
A .
a.
? ?
?
?
? AA
b. ? ?
?
??
? ? ? A B A B
c. ? ?
?
?
? KA KA
d. ? ?
?
??
? AB B A
Page 5
LINEAR ALGEBRA
MATRICES
A matrix is a rectangular array of numbers (or functions) enclosed in brackets. These numbers
(or function) are called entries of elements of the matrix.
Example:
??
??
??
2 0.4 8
5 -32 0
order = 2 x 3, 2 = no. of rows, 3 = no. of columns
Special Type of Matrices
1. Square Matrix
A m x n matrix is called as a square matrix if m = n i.e, no of rows = no. of columns
The elements
ij
a when i = j
? ?
11 22
a a ......... are called diagonal elements
Example:
??
??
??
12
45
2. Diagonal Matrix
A square matrix in which all non-diagonal elements are zero and diagonal elements may or
may not be zero.
Example:
??
??
??
10
05
Properties
a. diag [x, y, z] + diag [p, q, r] = diag [x + p, y + q, z + r]
b. diag [x, y, z] × diag [p, q, r] = diag [xp, yq, zr]
c.
? ?
?
??
?? ?
?? ??
??
1
1 1 1
diag x, y, z diag , ,
x y z
d.
? ?
??
??
t
diag x, y, z = diag [x, y, z]
e.
? ?
?? ?? ?
?? ??
n
n n n
diag x, y, z diag x ,y ,z
f. Eigen value of diag [x, y, z] = x, y & z
g. Determinant of diag [x, y, z] = xyz
3. Scalar Matrix
A diagonal matrix in which all diagonal elements are equal.
4. Identity Matrix
A diagonal matrix whose all diagonal elements are 1. Denoted by I
Properties
a. AI = IA = A
b.
?
n
II
c.
?
?
1
II
d. det(I) = 1
5. Null matrix
An m x n matrix whose all elements are zero. Denoted by O.
Properties:
a. A + O = O + A = A
b. A + (- A) = O
6. Upper Triangular Matrix
A square matrix whose lower off diagonal elements are zero.
Example:
??
??
??
??
??
3 4 5
0 6 7
0 0 9
7. Lower Triangular Matrix
A square matrix whose upper off diagonal elements are zero.
Example:
??
??
??
??
??
3 0 0
4 6 0
5 7 9
8. Idempotent Matrix
A matrix is called Idempotent if ?
2
AA
Example:
??
??
??
10
01
9. Involutary Matrix
A matrix is called Involutary if ?
2
AI .
Matrix Equality
Two matrices ? ?
? mn
A and ? ?
? p q
B are equal if
m = p ; n = q i.e., both have same size
ij
a =
ij
b for all values of i & j.
Addition of Matrices
For addition to be performed, the size of both matrices should be same.
If [C] = [A] + [B]
Then ??
ij ij ij
c a b
i.e., elements in same position in the two matrices are added.
Subtraction of Matrices
[C] = [A] – [B]
= [A] + [–B]
Difference is obtained by subtraction of all elements of B from elements of A.
Hence here also, same size matrices should be there.
Scalar Multiplication
The product of any m × n matrix A
??
??
??
jk
a and any scalar c, written as cA, is the m × n
matrix cA =
??
??
??
jk
ca obtained by multiplying each entry in A by c.
Multiplication of two matrices
Let ? ?
? m n
A and ? ?
? p q
B be two matrices and C = AB, then for multiplication, [n = p]
should hold. Then,
?
?
?
n
jk
j1
ik ij
C a b
Properties
? If AB exists then BA does not necessarily exists.
Example: ? ?
? 3 4
A , ? ?
? 4 5
B , then AB exits but BA does not exists as 5 ? 3
So, matrix multiplication is not commutative.
? Matrix multiplication is not associative.
A(BC) ? (AB)C .
? Matrix Multiplication is distributive with respect to matrix addition
A(B + C) = AB +AC
? If AB = AC ? B = C (if A is non-singular)
BA = CA ? B = C (if A is non-singular)
Transpose of a matrix
If we interchange the rows by columns of a matrix and vice versa we obtain transpose of a
matrix.
eg., A =
??
??
??
??
??
13
24
65
;
??
?
??
??
T
126
A
3 4 5
Conjugate of a matrix
The matrix obtained by replacing each element of matrix by its complex conjugate.
Properties
a.
? ?
? AA
b.
? ?
? ? ? A B A B
c.
? ?
? KA K A
d.
? ?
? AB AB
Transposed conjugate of a matrix
The transpose of conjugate of a matrix is called transposed conjugate. It is represented by
?
A .
a.
? ?
?
?
? AA
b. ? ?
?
??
? ? ? A B A B
c. ? ?
?
?
? KA KA
d. ? ?
?
??
? AB B A
Trace of matrix
Trace of a matrix is sum of all diagonal elements of the matrix.
Classification of real Matrix
a. Symmetric Matrix : ? ?
T
AA ?
b. Skew symmetric matrix : ? ?
T
AA ??
c. Orthogonal Matrix :
? ?
T 1 T
A A ; AA =I
?
?
Note:
a. If A & B are symmetric, then (A + B) & (A – B) are also symmetric
b. For any matrix
T
AA is always symmetric.
c. For any matrix,
??
??
??
??
T
A + A
2
is symmetric &
??
?
??
??
??
T
AA
2
is skew symmetric.
d. For orthogonal matrices, A1 ??
Classification of complex Matrices
a. Hermitian matrix :
? ?
AA
?
?
b. Skew – Hermitian matrix : AA
?
??
c. Unitary Matrix :
? ?
1
A A ;AA 1
? ? ?
??
Determinants
Determinants are only defined for square matrices.
For a 2 × 2 matrix
11 12
21 22
aa
aa
?? =
11 22 12 21
a a a a ?
Minors & co-factor
If
11 12 13
21 22 23
31 32 33
aaa
aaa
aaa
??
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