Prove: Provided it exists, (A-1)¯ = A.
Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
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![### Prove: Provided it exists, \((A^{-1})^{-1} = A\).
To prove this mathematical statement, we'll work through the concept of the inverse of a matrix.
1. **Definition of the Inverse Matrix:**
For a matrix \( A \), the inverse \( A^{-1} \) is defined such that:
\[
A \cdot A^{-1} = A^{-1} \cdot A = I
\]
where \( I \) is the identity matrix.
2. **Inverse of the Inverse Matrix:**
Given \( A \) is an invertible matrix, its inverse \( A^{-1} \) also has an inverse, denoted as \( (A^{-1})^{-1} \).
3. **Property of Matrix Inverses:**
The inverse of an inverse matrix should satisfy the original property of inverses. That is:
\[
A^{-1} \cdot (A^{-1})^{-1} = I
\]
and
\[
(A^{-1})^{-1} \cdot A^{-1} = I
\]
4. **Proof:**
By the definition of the inverse, multiplying \( A^{-1} \) by \( (A^{-1})^{-1} \) must yield the identity matrix:
\[
A^{-1} \cdot (A^{-1})^{-1} = I
\]
To retrieve the original matrix \( A \) from \( (A^{-1})^{-1} \), notice that:
\[
A \cdot A^{-1} = A^{-1} \cdot A = I
\]
implies that \( (A^{-1})^{-1} \) behaves in the same fashion as \( A \).
5. **Conclusion:**
Since \( (A^{-1})^{-1} \) satisfies the same property as \( A \), we can conclude:
\[
(A^{-1})^{-1} = A
\]
Thus, we have proved the given statement.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F3d1da097-c694-4dd7-b20d-f83f369c66d4%2F99a507a5-ae01-4a92-82cd-7b2ac0679156%2F9383sar.png&w=3840&q=75)
Transcribed Image Text:### Prove: Provided it exists, \((A^{-1})^{-1} = A\).
To prove this mathematical statement, we'll work through the concept of the inverse of a matrix.
1. **Definition of the Inverse Matrix:**
For a matrix \( A \), the inverse \( A^{-1} \) is defined such that:
\[
A \cdot A^{-1} = A^{-1} \cdot A = I
\]
where \( I \) is the identity matrix.
2. **Inverse of the Inverse Matrix:**
Given \( A \) is an invertible matrix, its inverse \( A^{-1} \) also has an inverse, denoted as \( (A^{-1})^{-1} \).
3. **Property of Matrix Inverses:**
The inverse of an inverse matrix should satisfy the original property of inverses. That is:
\[
A^{-1} \cdot (A^{-1})^{-1} = I
\]
and
\[
(A^{-1})^{-1} \cdot A^{-1} = I
\]
4. **Proof:**
By the definition of the inverse, multiplying \( A^{-1} \) by \( (A^{-1})^{-1} \) must yield the identity matrix:
\[
A^{-1} \cdot (A^{-1})^{-1} = I
\]
To retrieve the original matrix \( A \) from \( (A^{-1})^{-1} \), notice that:
\[
A \cdot A^{-1} = A^{-1} \cdot A = I
\]
implies that \( (A^{-1})^{-1} \) behaves in the same fashion as \( A \).
5. **Conclusion:**
Since \( (A^{-1})^{-1} \) satisfies the same property as \( A \), we can conclude:
\[
(A^{-1})^{-1} = A
\]
Thus, we have proved the given statement.
![**Matrix Multiplication and Scalar Addition Proof**
**Problem Statement:**
Prove the following matrix equation:
If \( a, b \in \mathbb{R} \) and \( P \) is a \( m \times n \) matrix, then the following equality holds:
\[ aP + bP = (a + b)P \]
**Explanation:**
Given scalars \( a \) and \( b \) in the set of real numbers \( \mathbb{R} \), and a matrix \( P \) of dimensions \( m \times n \):
- The term \( aP \) refers to the scalar multiplication of matrix \( P \) by the scalar \( a \).
- Similarly, \( bP \) is the scalar multiplication of matrix \( P \) by the scalar \( b \).
- The expression \( aP + bP \) involves the addition of these two resultant matrices.
**Proof:**
To prove the given equation, consider the operations involved:
1. **Scalar Multiplication:**
When a matrix \( P \) is multiplied by a scalar \( c \) (where \( c \) is either \( a \) or \( b \)):
\[ cP = c \begin{pmatrix}
p_{11} & p_{12} & \cdots & p_{1n} \\
p_{21} & p_{22} & \cdots & p_{2n} \\
\vdots & \vdots & \ddots & \vdots \\
p_{m1} & p_{m2} & \cdots & p_{mn}
\end{pmatrix}
= \begin{pmatrix}
cp_{11} & cp_{12} & \cdots & cp_{1n} \\
cp_{21} & cp_{22} & \cdots & cp_{2n} \\
\vdots & \vdots & \ddots & \vdots \\
cp_{m1} & cp_{m2} & \cdots & cp_{mn}
\end{pmatrix} \]
2. **Matrix Addition:**
Adding the resulting matrices \( aP \) and \( bP \):
\[ aP + bP = \begin{pmatrix}
ap_{11}](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F3d1da097-c694-4dd7-b20d-f83f369c66d4%2F99a507a5-ae01-4a92-82cd-7b2ac0679156%2Fcrg45yo.png&w=3840&q=75)
Transcribed Image Text:**Matrix Multiplication and Scalar Addition Proof**
**Problem Statement:**
Prove the following matrix equation:
If \( a, b \in \mathbb{R} \) and \( P \) is a \( m \times n \) matrix, then the following equality holds:
\[ aP + bP = (a + b)P \]
**Explanation:**
Given scalars \( a \) and \( b \) in the set of real numbers \( \mathbb{R} \), and a matrix \( P \) of dimensions \( m \times n \):
- The term \( aP \) refers to the scalar multiplication of matrix \( P \) by the scalar \( a \).
- Similarly, \( bP \) is the scalar multiplication of matrix \( P \) by the scalar \( b \).
- The expression \( aP + bP \) involves the addition of these two resultant matrices.
**Proof:**
To prove the given equation, consider the operations involved:
1. **Scalar Multiplication:**
When a matrix \( P \) is multiplied by a scalar \( c \) (where \( c \) is either \( a \) or \( b \)):
\[ cP = c \begin{pmatrix}
p_{11} & p_{12} & \cdots & p_{1n} \\
p_{21} & p_{22} & \cdots & p_{2n} \\
\vdots & \vdots & \ddots & \vdots \\
p_{m1} & p_{m2} & \cdots & p_{mn}
\end{pmatrix}
= \begin{pmatrix}
cp_{11} & cp_{12} & \cdots & cp_{1n} \\
cp_{21} & cp_{22} & \cdots & cp_{2n} \\
\vdots & \vdots & \ddots & \vdots \\
cp_{m1} & cp_{m2} & \cdots & cp_{mn}
\end{pmatrix} \]
2. **Matrix Addition:**
Adding the resulting matrices \( aP \) and \( bP \):
\[ aP + bP = \begin{pmatrix}
ap_{11}
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