/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 76 Prove that if \(A\) and \(B\) ar... [FREE SOLUTION] | 91Ó°ÊÓ

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Prove that if \(A\) and \(B\) are \(n \times n\) skew-symmetric matrices, then \(A+B\) is skew-symmetric.

Short Answer

Expert verified
The proof shows that if \( A \) and \( B \) are \( n \times n \) skew-symmetric matrices, then their sum \( C \) will also be a skew-symmetric matrix because of the properties of matrix algebra, particularly the transpose operation.

Step by step solution

01

Identify and recall skew-symmetric property of matrix

A square matrix \( A \) is skew-symmetric if \( A^T = -A \). Where, \( A^T \) is the transpose of matrix \( A \)
02

Express the sum of two skew-symmetric matrices

Let \( A \) and \( B \) denote the two n × n skew-symmetric matrices, therefore we express their sum as: another matrix \( C = A + B \)
03

Find the transpose of the sum

Let's find the transpose of the sum matrix \( C \). As per the properties of matrices: \( (A + B)^T = A^T + B^T \). This is equal to \( C^T = A^T + B^T \)
04

Substitute for the skew-symmetric matrices

Because it was given that \( A \) and \( B \) are skew-symmetric matrices, we can substitute \( A^T = -A \) and \( B^T = -B \) in the above equation: So, \( C^T = -A -B \). Which is equal to \( C^T = -C \)
05

Declare the resultant matrix as skew-symmetric

Since \( C^T = -C \), according to definition, the sum matrix \( C \) is skew-symmetric

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Matrix Transpose
When working with matrices, the concept of a transpose is fundamental. The transpose of a matrix, usually denoted as \( A^T \) for a matrix \( A \), is obtained by switching its rows and columns.
For example, if \( A \) is a 3x3 matrix:
  • The first row of \( A \) becomes the first column of \( A^T \)
  • The second row becomes the second column, and so on.
This operation might seem simple, but it plays a vital role in various matrix properties, such as in determining whether a matrix is symmetric or skew-symmetric.
In skew-symmetric matrices, the transpose has a very unique property: \( A^T = -A \). This means that each element \( a_{ij} \) of the matrix is the negative of the element \( a_{ji} \). Recognizing this pattern is what allows us to prove more nuanced properties in matrix algebra.
Linear Algebra
Linear algebra is a branch of mathematics concerning linear equations and their representations through matrices and vector spaces.
It is a foundational element of various applications, including computer graphics, engineering, physics, and more. Understanding how matrices operate and interact is critical in this field.
Matrices are rectangular arrays of numbers, symbols, or expressions. They offer a compact way to manage complex systems of equations. Linear algebra examines matrix behaviors, such as operations including addition, subtraction, and multiplication.
  • Adding or subtracting matrices requires them to be of the same dimensions. The corresponding entries from each matrix are combined directly.
  • Matrix multiplication is more involved, as it involves multiplying each row element from one matrix by the column element from another and summing the outcomes.
In our exercise, understanding how matrices, specifically skew-symmetric matrices, interact involves recognizing their properties under addition and transposition. This lays the ground for further exploration in the vast world of linear algebra.
Matrix Properties
Matrices come with specific properties, one of which is whether they are symmetric or skew-symmetric. A symmetric matrix is one where the transpose is equal to the original matrix, denoted \( A^T = A \).
Conversely, a skew-symmetric matrix has the specific defining property \( A^T = -A \). This indicates each matrix entry on one side of the main diagonal is the negative of the entry on the other side.
Such properties help in determining different characteristics of matrix operations. In the case of skew-symmetric matrices, an interesting property arises when adding two such matrices:
  • If both matrices \( A \) and \( B \) satisfy \( A^T = -A \) and \( B^T = -B \), their sum \( C = A + B \) will also be skew-symmetric.
  • This is because the transpose of the sum, \( (A + B)^T = A^T + B^T \), will equal \( -A - B \), which is simply \( -C \).
Understanding these properties is crucial because it makes it easier to work with matrices, especially when dealing with more complex linear algebra problems or when proving certain characteristics as in our exercise.

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Most popular questions from this chapter

Perform the operations, given \(a=3, b=-4,\) and \(A=\left[\begin{array}{ll}1 & 2 \\\ 3 & 4\end{array}\right], \quad B=\left[\begin{array}{rr}0 & 1 \\ -1 & 2\end{array}\right], \quad O=\left[\begin{array}{ll}0 & 0 \\ 0 & 0\end{array}\right]\). $$(a-b)(A-B)$$.

Find (a) \(A^{T} A\) and (b) \(A A^{T} .\) Show that each of these products is symmetric. $$ A=\left[\begin{array}{rrrr}4 & -3 & 2 & 0 \\\2 & 0 & 11 & -1 \\\\-1 & -2 & 0 & 3 \\\14 & -2 & 12 & -9 \\\6 & 8 & -5 & 4 \end{array}\right] $$

Perform the operations, given \(c=-2\) and \(A=\left[\begin{array}{rrr}1 & 2 & 3 \\\ 0 & 1 & -1\end{array}\right], B=\left[\begin{array}{rr}1 & 3 \\ -1 & 2\end{array}\right], C=\left[\begin{array}{rr}0 & 1 \\ -1 & 0\end{array}\right]\). $$(B+C) A$$.

Wildlife \(A\) wildlife management team studied the reproduction rates of deer in three tracts of a wildlife preserve. The team recorded the number of females \(x\) in each tract and the percent of females \(y\) in each tract that had offspring the following year. The table shows the results. $$ \begin{array}{l|ccc} \hline \text {Number, }, x & 100 & 120 & 140 \\ \text {Percent, } y & 75 & 68 & 55 \\ \hline \end{array} $$ (a) Find the least squares regression line for the data. (b) Use a graphing utility to graph the model and the data in the same viewing window. (c) Use the model to create a table of estimated values for y. Compare the estimated values with the actual data. (d) Use the model to estimate the percent of females that had offspring when there were 170 females. (e) Use the model to estimate the number of females when \(40 \%\) of the females had offspring.

Perform the operations, given \(c=-2\) and \(A=\left[\begin{array}{rrr}1 & 2 & 3 \\\ 0 & 1 & -1\end{array}\right], B=\left[\begin{array}{rr}1 & 3 \\ -1 & 2\end{array}\right], C=\left[\begin{array}{rr}0 & 1 \\ -1 & 0\end{array}\right]\). $$c(B A)$$.

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