# What are the eigenvalues of a real symmetric matrix?

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## What are the eigenvalues of a real symmetric matrix?

▶ All eigenvalues of a real symmetric matrix are real. orthogonal. complex matrices of type A ∈ Cn×n, where C is the set of complex numbers z = x + iy where x and y are the real and imaginary part of z and i = √ −1. and similarly Cn×n is the set of n × n matrices with complex numbers as its entries.

## Does a 3×3 matrix always have a real eigenvalue?

The characteristic polynomial is a cubic polynomial. Every cubic polynomial with real coefficients has at least one real root. Hence every real 3×3 matrix has at least one real eigenvalue, and obviously, a corresponding eigenvector in R3.

Can a symmetric matrix have any eigenvalues that are zero?

I know that a non-zero symmetric 2×2 matrix can’t have only zero eigenvalues ( a zero eigenvalue with algebraic multiplicity 2), since such a matrix should have complex off diagonal entries to satisfy both trace and determinant being zero.

### What is the determinant of a symmetric matrix?

If you view symmetric matrices as quadratic polynomials, the determinant of the associated symmetric matrix is actually the discriminant of the quadratic form. The discriminant is also the equation of the dual variety to the quadratic Veronese variety , which is irreducible via the bi-duality theorem.

### What are the eigenvectors of an identity matrix?

The following are the steps to find eigenvectors of a matrix: Determine the eigenvalues of the given matrix A using the equation det (A – λI) = 0, where I is equivalent order identity matrix as A. Substitute the value of λ1​ in equation AX = λ1​ X or (A – λ1​ I) X = O. Calculate the value of eigenvector X which is associated with eigenvalue λ1​. Repeat steps 3 and 4 for other eigenvalues λ2​, λ3​, as well.

What does eigenbasis mean?

Eigenbasis meaning (mathematics) A basis for a vector space consisting entirely of eigenvectors.