**Introduction to Multiplicative Inverse of a Matrix**

Exercise.1.5:A square matrix is said to be invertible if it has a multiplicative inverse. The multiplicative inverse of a square matrix *A* is a square matrix *B* such that *AB*=*BA*=*I*, where *I* is the identity matrix.

Not all square matrices are invertible. A square matrix is invertible if and only if its determinant is nonzero. The determinant of a matrix can be calculated using various methods, such as Cramer’s rule or Gaussian elimination.

To find the multiplicative inverse of a square matrix *A*, we can use the following steps:

- Calculate the determinant of
*A*. - If the determinant of
*A*is nonzero, then*A*is invertible. - To find the multiplicative inverse of
*A*, we can use the following formula:

A^{-1} = (1 / det(A)) * adj(A)

where *adj*(*A*) is the adjoint of *A*. The adjoint of a matrix is obtained by transposing the matrix and then replacing each entry with its cofactor.

The following is an example of how to find the multiplicative inverse of a square matrix:

A = [[1, 2], [3, 4]]

det(A) = -1

adj(A) = [[-4, 3], [2, -1]]

A^{-1} = (1 / -1) * [[-4, 3], [2, -1]] = [[4, -3], [-2, 1]]

The multiplicative inverse of a matrix has many applications in mathematics and science. For example, it can be used to solve systems of linear equations, invert functions, and calculate least squares solutions.

**Exercise 1.5 in 9th Class Mathematics**

Exercise 1.5 in 9th Class Mathematics contains a number of questions on the multiplicative inverse of a matrix. For example, one question asks students to find the multiplicative inverse of the following matrix:

A = [[1, 2], [3, 4]]

The answer to this question is the matrix *A*−1 that we calculated above:

A^{-1} = [[4, -3], [-2, 1]]

Another question in Exercise 1.5 asks students to show that the multiplicative inverse of the identity matrix is the identity matrix itself. This can be shown by the following calculation:

(I * I) = I

where *I* is the identity matrix.

Students should be able to solve all of the questions in Exercise 1.5 by using the concepts and methods that they have learned about the multiplicative inverse of a matrix.

__Singular Matrix:__

A singular matrix, also known as a non-invertible or degenerate matrix, is a square matrix that does not have a multiplicative inverse. In other words, a matrix is singular if and only if its determinant is equal to zero. When you attempt to find the multiplicative inverse of a singular matrix, it cannot be found because the division by zero is undefined.

Mathematically, a square matrix A is singular if and only if det(A) = 0, where “det(A)” represents the determinant of matrix A.

**Non-Singular Matrix:**

Conversely, a non-singular matrix, also known as an invertible or non-degenerate matrix, is a square matrix that does have a multiplicative inverse. In this case, the determinant of the matrix is not zero. A non-singular matrix can be inverted, and its inverse can be found, which allows you to perform operations equivalent to division in the context of matrix algebra. Exercise.1.5:

Mathematically, a square matrix A is non-singular if and only if det(A) is not equal to zero, indicating that the matrix has a unique multiplicative inverse.

In the realm of mathematics, matrices play a fundamental role in various applications, from solving systems of linear equations to representing data in various fields.

In this exercise, we delve into the intriguing concept of the “Multiplicative Inverse of a Matrix.” Just as real numbers have their inverses, matrices, too, have a counterpart – a matrix that, when multiplied with the original, yields the identity matrix.

Understanding the multiplicative inverse of a matrix is not only a valuable mathematical skill but also a crucial tool for solving diverse real-world problems.

Whether you are exploring physics, engineering, computer science, or economics, the ability to find the multiplicative inverse of a matrix can be a game-changer.

In this exercise, we will embark on a journey to uncover the properties, conditions, and methods for determining the multiplicative inverse of a matrix.

You will learn how to recognize when a matrix has a multiplicative inverse and how to calculate it effectively.

With practice and understanding, you will master this concept, enhancing your problem-solving capabilities and broadening your mathematical toolkit.

So, let’s embark on this exciting mathematical adventure and explore the multiplicative inverse of matrices.

By the end of this exercise, you will have acquired a powerful skill that can open doors to a wide range of mathematical and practical applications.

The multiplicative inverse of a matrix is a matrix that, when multiplied by the original matrix, results in the identity matrix. The identity matrix is a square matrix with ones on the diagonal and zeros elsewhere.

In other words, the multiplicative inverse of a matrix *A* is a matrix *B* such that:

`AB = BA = I`

where *I* is the identity matrix.

Not all matrices have multiplicative inverses. Only matrices with nonzero determinants are invertible. The determinant of a matrix can be calculated using various methods, such as Cramer’s rule or Gaussian elimination.

To find the multiplicative inverse of an invertible matrix *A*, we can use the following formula:

`A^{-1} = (1 / det(A)) * adj(A)`

where *adj*(*A*) is the adjoint of *A*. The adjoint of a matrix is obtained by transposing the matrix and then replacing each entry with its cofactor. Exercise.1.5:

The multiplicative inverse of a matrix has many applications in mathematics and science. For example, it can be used to solve systems of linear equations, invert functions, and calculate least squares solutions.

#### Questions & Answers

**Questions and Answers about Multiplicative Inverse of Matrix**

Q: What is the multiplicative inverse of a matrix?

A: The multiplicative inverse of a matrix *A* is a matrix *B* such that *AB*=*BA*=*I*, where *I* is the identity matrix.

Q: Not all matrices have multiplicative inverses. Why?

A: A matrix has a multiplicative inverse if and only if its determinant is nonzero. The determinant of a matrix is a measure of how much a matrix stretches or shrinks space. If the determinant is zero, then the matrix is either singular (meaning that it does not have a full set of linearly independent columns) or degenerate (meaning that it has a zero eigenvalue). In either case, the matrix does not have a multiplicative inverse.

Q: How do I find the multiplicative inverse of a matrix?

A: To find the multiplicative inverse of a matrix *A*, you can use the following formula:

A^{-1} = (1 / det(A)) * adj(A)

where *adj*(*A*) is the adjoint of *A*. The adjoint of a matrix is obtained by transposing the matrix and then replacing each entry with its cofactor.

Q: What are some of the applications of the multiplicative inverse of a matrix?

A: The multiplicative inverse of a matrix has many applications in mathematics and science. For example, it can be used to:

- Solve systems of linear equations
- Invert functions
- Calculate least squares solutions
- Compute the determinant of a matrix
- Calculate the eigenvalues and eigenvectors of a matrix
- Perform matrix multiplication

Q: Give me an example of the multiplicative inverse of a matrix.

A: Consider the following matrix:

A = [[1, 2], [3, 4]]

The determinant of *A* is -1, and the adjoint of *A* is [[-4, 3], [2, -1]]. Therefore, the multiplicative inverse of *A* is:

A^{-1} = (1 / -1) * [[-4, 3], [2, -1]] = [[4, -3], [-2, 1]]

**Question 1:**What is the multiplicative inverse of a matrix?**Answer:**The multiplicative inverse of a matrix is a special matrix that, when multiplied by the original matrix, results in the identity matrix. It is denoted as A^(-1), and it satisfies the equation A * A^(-1) = A^(-1) * A = I, where A represents the original matrix, A^(-1) is the multiplicative inverse, and I is the identity matrix.**Question 2:**Which matrices have a multiplicative inverse?**Answer:**Only square matrices, meaning matrices with the same number of rows and columns, can have a multiplicative inverse. However, not all square matrices have a multiplicative inverse. A square matrix must be non-singular, meaning its determinant is non-zero, to have a multiplicative inverse.**Question 3:**How do you find the multiplicative inverse of a matrix?**Answer:**To find the multiplicative inverse of a square matrix A, you can use several methods. One common approach is to use the formula:- A^(-1) = (1 / det(A)) * adj(A)
- Where “det(A)” is the determinant of matrix A, and “adj(A)” is the adjugate (or adjoint) of matrix A. The adjugate is obtained by finding the transpose of the cofactor matrix of A.
**Question 4:**What is the significance of the multiplicative inverse of a matrix?**Answer:**The multiplicative inverse of a matrix is a crucial concept in linear algebra and has various practical applications. It is used for solving systems of linear equations, transforming matrices, and finding solutions to matrix equations. In essence, it allows us to “divide” by a matrix, just as we would divide by a number, in the context of solving equations.**Question 5:**Can a matrix have more than one multiplicative inverse?**Answer:**No, a square matrix can have at most one multiplicative inverse. If a matrix has a multiplicative inverse, it is unique. However, not all matrices have a multiplicative inverse, and some matrices may not have one due to their singular nature (determinant equal to zero).**Question 6:**What is the multiplicative inverse of the identity matrix?**Answer:**The multiplicative inverse of the identity matrix (I) is the identity matrix itself. In other words, I^(-1) = I. This is because when the identity matrix is multiplied by itself, it results in the same identity matrix.

The multiplicative inverse of a matrix is a powerful tool that has many applications in mathematics and science. It can be used to solve systems of linear equations, invert functions, calculate least squares solutions, and perform many other operations.

The following are some of the key points about the multiplicative inverse of a matrix:

- Not all matrices have multiplicative inverses. A matrix has a multiplicative inverse if and only if its determinant is nonzero. Exercise.1.5:
- The multiplicative inverse of a matrix can be found using the following formula:
- A^{-1} = (1 / det(A)) * adj(A)
- where
*adj*(*A*) is the adjoint of*A*. - The multiplicative inverse of a matrix has many applications, including:
- Solving systems of linear equations
- Inverting functions
- Calculating least squares solutions
- Computing the determinant of a matrix
- Calculating the eigenvalues and eigenvectors of a matrix
- Performing matrix multiplication

The multiplicative inverse of a matrix is an essential concept in linear algebra and has many important applications in other areas of mathematics and science.

#### Conclusion

The multiplicative inverse of a matrix is a powerful tool that can be used to solve a wide range of problems. It is important to understand the concept of the multiplicative inverse and how to find it, as it is a fundamental tool in many areas of mathematics and science.

The concept of the multiplicative inverse of a matrix is a fundamental and powerful idea in the realm of linear algebra. It offers a key tool for solving a wide array of mathematical problems and has significant practical applications in various fields.

In our exploration of the multiplicative inverse of a matrix, we’ve learned that not all matrices possess this unique counterpart. Only square matrices that are non-singular, or in other words, those with a non-zero determinant, can have a multiplicative inverse. This property distinguishes them from matrices that do not possess this inverse.

Discovering the multiplicative inverse involves methods such as finding the determinant and the adjugate of the matrix, ultimately leading us to a matrix that, when multiplied with the original, yields the identity matrix. This inverse matrix allows us to “divide” by matrices, a concept akin to solving equations in the world of numbers. Exercise.1.5:

The significance of the multiplicative inverse extends to numerous applications, including solving systems of linear equations, transformations, and solving matrix equations. It empowers us to manipulate matrices in a way that simplifies complex operations and problem-solving.

While the concept may seem abstract at first, it is a fundamental pillar of mathematics and has real-world implications. As we conclude our exploration of the multiplicative inverse of a matrix, we have gained a valuable mathematical skill, one that enhances our problem-solving capabilities and equips us with a versatile tool for tackling a broad range of mathematical challenges. This concept continues to be at the core of many mathematical and practical endeavors, making it an indispensable part of our mathematical toolkit.

** Suggested Read:**

- Exercise 1.1: Introduction to matrices
- Exercise.1.2. Types Of Matrices.
**Exercise 1.3: Addition And Subtraction Of Matrices****Exercise.1.4: Multiplication Of Matrices****Exercise 4.1: Introduction to Algebraic Expressions****Exercise 4.2: Introduction to Algebraic Expressions****Exercise 4.3: Introduction to Algebraic Expressions**- Explanation of Abstract Algebra Problems
- Easy Way to Learn A Cubed minus B Cubed
- Best 7th Grade Math Formulas for Children
- Derivation of A Square Minus B Square With Example
- Types of A Specific Formula for Solving a Problem Is Called

**Full Book 9th Math **

**Exercise #1.5**

**Azam Bodla**

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