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Eigenvalue Eigenvector Calculator

Calculate eigenvalues and eigenvectors of 2x2 and 3x3 matrices with characteristic polynomial derivation and step-by-step solutions.

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What Are Eigenvalues and Eigenvectors?

For a square matrix $A$, an eigenvector $\mathbf{v}$ and eigenvalue $\lambda$ satisfy $A\mathbf{v} = \lambda\mathbf{v}$. Eigenvalues reveal scaling behavior; eigenvectors show the directions that stay aligned under the transformation.

Characteristic Equation

$$\det(A - \lambda I) = 0$$

For a $2 \times 2$ matrix this yields a quadratic polynomial. For $3 \times 3$, a cubic polynomial whose roots are the eigenvalues.

Finding Eigenvectors

For each eigenvalue $\lambda$, solve $(A - \lambda I)\mathbf{v} = \mathbf{0}$ using row reduction. The resulting nonzero vector (normalized) is an eigenvector.

Related tools: Matrix Determinant Calculator and Column Space Calculator.

Frequently Asked Questions

Can eigenvalues be complex?

Yes. Real matrices can have complex conjugate eigenvalue pairs. This calculator handles complex roots for $2 \times 2$ matrices and reports them in $a + bi$ form.

What is the trace of a matrix?

The trace is the sum of diagonal entries. It equals the sum of all eigenvalues (including complex parts).

When are eigenvectors useful?

Eigenanalysis appears in physics (vibrations), data science (PCA), graph theory, differential equations, and stability analysis of dynamical systems.

Why normalize eigenvectors?

Eigenvectors are defined up to a scalar multiple. Normalizing to unit length gives a standard representative for display and comparison.