Math Problem Statement

Prove that the product of a matrix and its transpose is a symmetric matrix.

Solution

The image shows the following mathematical problem:

"g) Prove that the product of a matrix and its transpose is a symmetric matrix."

Proof:

Let AA be an arbitrary matrix, and we want to show that the product AATA A^T is a symmetric matrix.

A matrix BB is said to be symmetric if B=BTB = B^T. So, we need to prove that (AAT)T=AAT(A A^T)^T = A A^T.

  1. Transpose of a Product: One property of the transpose operation is that (AB)T=BTAT(A B)^T = B^T A^T for any two matrices AA and BB. Applying this to the product AATA A^T, we get: (AAT)T=(AT)TAT(A A^T)^T = (A^T)^T A^T

  2. Transpose of the Transpose: Another property is that the transpose of a transpose is the original matrix, i.e., (AT)T=A(A^T)^T = A. So we have: (AAT)T=AAT(A A^T)^T = A A^T

Since (AAT)T=AAT(A A^T)^T = A A^T, we have shown that the product AATA A^T is a symmetric matrix.

Conclusion:

The product of any matrix and its transpose is always a symmetric matrix.


Do you need more details on any of the steps? Here are some related questions that might interest you:

  1. What is the definition of a transpose of a matrix?
  2. Can the product ATAA^T A (instead of AATA A^T) also be symmetric?
  3. What are the conditions for a matrix to be symmetric?
  4. How does the transpose

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Math Problem Analysis

Mathematical Concepts

Matrix Algebra
Transpose of a Matrix
Symmetric Matrix

Formulas

Transpose of a product: (A * B)^T = B^T * A^T
Transpose of a transpose: (A^T)^T = A

Theorems

Definition of a Symmetric Matrix
Properties of Transpose

Suitable Grade Level

Undergraduate Mathematics