Chapter 7: Problem 6
Find the singular values of the given matrix. $$A=\left[\begin{array}{ll} 3 & 4 \end{array}\right]$$
Short Answer
Expert verified
The singular values of the matrix are 5 and 0.
Step by step solution
01
Compute A Transpose times A
To find the singular values of matrix \(A\), we first compute \(A^TA\). Matrix \(A\) is \( [3\ 4] \), thus its transpose \(A^T\) is \( \begin{bmatrix} 3 \ 4 \end{bmatrix} \). Compute the multiplication:\[A^TA = \begin{bmatrix} 3 \ 4 \end{bmatrix} \begin{bmatrix} 3 & 4 \end{bmatrix} = \begin{bmatrix} 3 & 4 \ 4 \ 3 \end{bmatrix} \begin{bmatrix} 3 & 4 \end{bmatrix}= \begin{bmatrix} 9 & 12 \ 12 & 16 \end{bmatrix}\]
02
Solve the Characteristic Equation
To find the singular values, we solve the characteristic equation \( \det(A^TA - \lambda I) = 0 \), where \( I \) is the identity matrix. Let's find this determinant:\[\det \begin{bmatrix} 9 - \lambda & 12 \ 12 & 16 - \lambda \end{bmatrix} = (9-\lambda)(16-\lambda) - (12)(12)\]
03
Expand and Simplify the Determinant
Start simplifying the determinant:\[(9-\lambda)(16-\lambda) - 144 = 144 - 25\lambda + \lambda^2 - 144 = \lambda^2 - 25\lambda\]So, the characteristic equation becomes \( \lambda^2 - 25\lambda = 0 \).
04
Solve for Eigenvalues
Factor the equation \( \lambda^2 - 25\lambda = 0 \):\[\lambda(\lambda - 25) = 0\]The solutions are \( \lambda_1 = 25 \) and \( \lambda_2 = 0 \).
05
Compute Singular Values
The singular values \( \sigma \) are the square roots of the non-zero eigenvalues of \( A^TA \). Thus, we take the square root of \( \lambda_1 = 25 \):\[ \sigma_1 = \sqrt{25} = 5\]Therefore, the singular values of \( A \) are 5 and 0.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Characteristic Equation
The characteristic equation is a fundamental part of linear algebra, used to find eigenvalues of a matrix. It is derived from the determinant of the matrix. For a square matrix, say matrix \( A \), the characteristic equation is formulated as \( \det(A - \lambda I) = 0 \), where \( \lambda \) represents eigenvalues and \( I \) is the identity matrix with the same dimensions as \( A \). This equation essentially allows us to discover the inherent properties of a matrix by solving for \( \lambda \). These solutions are crucial to understanding transformations represented by matrices, finding singular values, and performing various matrix computations.
- The characteristic equation is essential in computing matrices' eigenvalues.
- It assists in analyzing matrices’ structural behaviors.
Eigenvalues
Eigenvalues are special numbers associated with matrices that offer wonderful insights into the characteristics and transformations of the matrix. When a matrix acts on a vector, it often stretches or compresses it, and eigenvalues tell us exactly how much a vector is stretched or compressed without altering its direction. To find eigenvalues, we solve the characteristic equation of the matrix.
Imagine you have a square matrix \( A \). Solving \( \det(A - \lambda I) = 0 \) for \( \lambda \) gives the eigenvalues.
Imagine you have a square matrix \( A \). Solving \( \det(A - \lambda I) = 0 \) for \( \lambda \) gives the eigenvalues.
- Eigenvalues demonstrate how much a vector is scaled during transformation.
- They are crucial in various physics and engineering problems to understand systems' behaviors.
Matrix Transpose
The transpose of a matrix is a simple yet powerful operation that flips a matrix over its diagonal, swapping the rows and columns. For a given matrix \( A \), the transpose, denoted as \( A^T \), has its elements corrected as follows: the element located in the \( i \)-th row and \( j \)-th column of \( A \) becomes the element in the \( j \)-th row and \( i \)-th column of \( A^T \).
- Transposing is integral in various linear algebra computations, preparing matrices for multiplication, or other operations.
- It is often used to ensure dimensions align in processings like finding inner products.
Determinant
The determinant is a scalar value that can be computed from a square matrix and provides important insights into the matrix’s properties. For a matrix \( A \), the determinant, denoted as \( \det(A) \), can indicate whether a matrix is invertible and its volume scaling factor in space transformations.
The computation of a determinant varies with matrix size but generally involves summing the products of elements and their minors. In singular value calculations, as in our step-by-step process, determinants become useful in solving the characteristic equation.
The computation of a determinant varies with matrix size but generally involves summing the products of elements and their minors. In singular value calculations, as in our step-by-step process, determinants become useful in solving the characteristic equation.
- The determinant helps in checking matrix invertibility.
- It is instrumental in systems solving, eigenvalue determination, and transformation analysis.