Is a Matrix Symmetric if Row Space Equals Column Space?

This means that the transpose of A is not equal to A. Therefore, the statement "If the row space equals the column space, then AT=A" is false. In summary, the statement "If the row space equals the column space, then AT=A" is false because the matrix is not symmetric.
  • #1
chaotixmonjuish
287
0
I had this question on a test and I was wondering why it is false:

If the row space equals teh column space then AT=A.
 
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  • #2
Consider the matrix
[tex]\left(\begin{array}{cc}1 & 1\\0 & 1\end{array}\right)[/tex].
 
  • #3
Ok, so I had a rationale why it was false but I'm not sure if I am close.

Obviously here the AT does not equal A, but the dimension of the row space equals column space equals 2. Is this the right reasoning?
 
  • #4
chaotixmonjuish said:
Ok, so I had a rationale why it was false but I'm not sure if I am close.

Obviously here the AT does not equal A, but the dimension of the row space equals column space equals 2. Is this the right reasoning?

Well, the row space and the column space are both R2, but the matrix is not symmetric.
 

What is a symmetric matrix?

A symmetric matrix is a square matrix that is equal to its transpose. In other words, it is a matrix that is symmetric along its main diagonal.

What are the properties of a symmetric matrix?

Some important properties of a symmetric matrix include: it has equal eigenvalues, it is diagonalizable, and its eigenvectors are mutually orthogonal.

How do you determine if a matrix is symmetric?

To determine if a matrix is symmetric, you can check if it is equal to its transpose. If the elements are the same when reflected across the main diagonal, then it is symmetric.

What is the significance of symmetric matrices in mathematics?

Symmetric matrices have many applications in mathematics, including in linear algebra, optimization, and statistics. They are also important in physics and engineering, where they are used to represent real-world systems.

What are some examples of symmetric matrices?

Some examples of symmetric matrices include identity matrices, diagonal matrices, and matrices with all equal elements. In real-world applications, symmetric matrices can be used to represent symmetric systems, such as in mechanics or quantum mechanics.

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