# What is the difference between diagonalization and orthogonal diagonalization?

## What is the difference between diagonalization and orthogonal diagonalization?

A matrix P is called orthogonal if P−1=PT. Thus the first statement is just diagonalization while the one with PDPT is actually the exact same statement as the first one, but in the second case the matrix P happens to be orthogonal, hence the term “orthogonal diagonalization”.

How do you do orthogonal diagonalization?

(P−1)−1 = P = (PT )T = (P−1)T shows that P−1 is orthogonal. An n×n matrix A is said to be orthogonally diagonalizable when an orthogonal matrix P can be found such that P−1AP = PT AP is diagonal. This condition turns out to characterize the symmetric matrices.

### Is an orthogonally diagonalizable matrix symmetric?

A real square matrix A is orthogonally diagonalizable if there exist an orthogonal matrix U and a diagonal matrix D such that A=UDUT. Orthogonalization is used quite extensively in certain statistical analyses. An orthogonally diagonalizable matrix is necessarily symmetric.

Is orthogonal diagonalization unique?

So diagonalization is not unique in general, but unique up to permutation of the diagonal entries in D, and multiples of the columns of U.

## What is diagonalization of symmetric matrix?

Diagonalization of symmetric matrices. Theorem: A real matrix A is symmetric if and only if A can be diagonalized by an orthogonal matrix, i.e. A = UDU−1 with U orthogonal and D diagonal.

How do you know if a matrix is orthogonal?

To check if a given matrix is orthogonal, first find the transpose of that matrix. Then, multiply the given matrix with the transpose. Now, if the product is an identity matrix, the given matrix is orthogonal, otherwise, not.

### Are all orthogonal matrices symmetric?

All the orthogonal matrices are symmetric in nature. (A symmetric matrix is a square matrix whose transpose is the same as that of the matrix).

How do you know if a diagonal matrix is orthogonally similar?

Definition: An n×n n × n matrix A is said to be orthogonally diagonalizable if there are an orthogonal matrix P (with P−1=PT P − 1 = P T and P has orthonormal columns) and a diagonal matrix D such that A=PDPT=PDP−1 A = P D P T = P D P − 1 .

## Is orthogonal matrix symmetric?

The orthogonal matrix is always a symmetric matrix. All identity matrices are hence the orthogonal matrix. The product of two orthogonal matrices will also be an orthogonal matrix. The transpose of the orthogonal matrix will also be an orthogonal matrix.

Is every orthogonal matrix orthogonally diagonalizable?

Therefore, every symmetric matrix is diagonalizable because if U is an orthogonal matrix, it is invertible and its inverse is UT. In this case, we say that A is orthogonally diagonalizable. Therefore every symmetric matrix is in fact orthogonally diagonalizable.