# How to calculate eigenvector

Eigenvalues and eigenvectors are essential components of linear algebra with numerous applications in various fields such as physics, computer science, and engineering. In this article, we will discuss the process of calculating eigenvectors for a given square matrix.

**Step 1: Find the Eigenvalues**

1.1 To find eigenvectors, we first need to calculate the eigenvalues of a given matrix A. This involves solving the characteristic equation, which is defined as det(A – λ*I) = 0, where λ represents the eigenvalue and I is the identity matrix of the same dimensions as A.

1.2 Calculate the determinant and solve for the values of λ.

**Step 2: Solve for Eigenvectors**

2.1 For each eigenvalue found in Step 1, form a new equation (A – λ*I)v = 0, where v is the eigenvector corresponding to the eigenvalue λ.

2.2 Manipulate the equations into an augmented matrix form by appending a zero column vector on the right-hand side of each row.

2.3 Apply Gaussian elimination, reducing the original matrix to its row echelon form.

2.4 Create a system of linear equations by using rows from row echelon form of the augmented matrix.

2.5 Solve these linear equations using back substitution or other methods.

2.6 Derive as many basic variables as constraints permit and assign free variables as necessary.

2.7 Express each basic variable in terms of free variables.

2.8 Normalization (optional): Divide each eigenvector by its magnitude to obtain unit eigenvectors.

**Example:**

Let’s calculate eigenvectors for a 2×2 matrix.

A = | 4 3 |

| 0 -1|

**Step 1:**

Solving det(A – λ*I) = 0, we find the eigenvalues λ1 = 4 and λ2 = -1.

**Step 2:**

Using λ1 = 4: (A – λ1*I)v = (A – 4I)v =

| 0 3 | | v1 | | 0 |

| 0 -5 | | v2 | = | 0 |

v1 is a free variable and v2 can be expressed by the equation -5v2 = 0. Thus, eigenvector corresponding to λ1 is (1, 0).

Using λ2 = -1: (A – λ2 * I)v = (A + I)v =

| 5 3 | | v3 | | 0 |

| 0 0 | | v4 | = | 0 |

Now, v3 and v4 are free variables resulting in an infinite family of eigenvectors for λ2. We can take one eigenvector for our purposes, such as (-3,5).

**Conclusion:**

Understanding how to calculate eigenvectors is an essential skill for anyone studying linear algebra or working with data-driven applications. Practicing this method will solidify your understanding of eigenvectors and improve your problem-solving abilities in various domains.