Prove Orthogonal Matrix Transpose is Orthogonal

In summary, proving that the transpose of an orthogonal matrix is an orthogonal matrix involves using the Kronecker delta and knowing the definition of an orthogonal matrix. It is important to include this information in the initial post to avoid confusion and to provide evidence of understanding. Additionally, there is another definition of an orthogonal matrix that is more common and useful in this case, which involves the columns being mutually orthogonal.
  • #1
Dustinsfl
2,281
5
Prove that the transpose of an orthogonal matrix is an orthogonal matrix.

I think that the Kronecker delta needs to be used but not sure how to write it out.
 
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  • #2
Do you know the definition of an orthogonal matrix?
 
  • #3
The columns most for an orthogonal set.
 
  • #4
Dustinsfl said:
The columns most for an orthogonal set.
Wouldn't that be information you should include in your first post, as either given/known data or relevant equations?

That's why those sections are in the problem template. We shouldn't have to pry that information out of you.
 
  • #5
Mark44 said:
Wouldn't that be information you should include in your first post, as either given/known data or relevant equations?

I find that trivial because if I didn't know that, why would I be trying to prove anything related to orthogonal matrices?
 
  • #6
How do we know that you know that? Our only evidence of what you know or don't know is the information you include.
 
  • #7
Because I have no business trying to prove something I know nothing about.
 
  • #8
So convince us that you know something about it by including the basic information when you post.
 
  • #9
There's another definition of "orthogonal matrix" that's more common (I think), and definitely more useful in this case. (It makes the problem trivial). Do you know any other statements about orthogonal matrices? Something that holds if, and only if, the columns are mutually orthogonal?
 

FAQ: Prove Orthogonal Matrix Transpose is Orthogonal

What is an orthogonal matrix?

An orthogonal matrix is a square matrix whose columns and rows are orthogonal unit vectors. This means that the dot product of any two columns or rows is equal to zero, and the norm (length) of each column or row is equal to one. Orthogonal matrices are important in linear algebra because they preserve the length and angle of vectors, making them useful for transformations and solving systems of equations.

What is the transpose of a matrix?

The transpose of a matrix is a new matrix where the rows and columns are flipped. This means that the first row becomes the first column, the second row becomes the second column, and so on. More generally, the element in the i-th row and j-th column of the original matrix becomes the element in the j-th row and i-th column of the transposed matrix. The transpose of a matrix is denoted by a superscript "T" next to the matrix (e.g. AT).

How do you prove that an orthogonal matrix transpose is orthogonal?

To prove that the transpose of an orthogonal matrix is orthogonal, we need to show that the dot product of any two columns or rows is equal to zero, and the norm of each column or row is equal to one. This can be done by using the definition of the transpose and the properties of dot products and norms.

Why is it important to prove that an orthogonal matrix transpose is orthogonal?

Proving that an orthogonal matrix transpose is orthogonal is important because it confirms that the matrix preserves the length and angle of vectors. This is useful in many applications, such as solving systems of equations, performing rotations and reflections, and in computer graphics and machine learning.

Can an orthogonal matrix transpose be a non-square matrix?

No, an orthogonal matrix transpose can only be a square matrix. This is because the transpose operation only flips the rows and columns of a matrix, so the resulting matrix will always have the same number of rows and columns as the original matrix. Since orthogonal matrices are always square matrices, their transpose will also be a square matrix.

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