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Eigenvectors – Definition With Examples

Jo-ann Caballes

Updated on January 9, 2024

Welcome to Brighterly, your go-to source for making math fun and understandable for children. In this article, we’re diving into the world of eigenvectors. At Brighterly, we believe in simplifying complex concepts, making them accessible to young minds. Eigenvectors are a key part of linear algebra, and understanding them can be a stepping stone to more advanced mathematical concepts. Let’s break down what eigenvectors are, how to find them, their properties, and see them in action with real-world applications and simple examples. Get ready to explore math in a way that’s engaging and educational!

What are Eigenvectors of a Matrix?

Eigenvectors are special vectors that are linked to matrices. They have a unique property: when a matrix is applied to an eigenvector, the direction of the vector doesn’t change. Instead, it might get stretched or shrunk by a certain amount, which is called the eigenvalue. We represent this idea with a simple equation: Av=λv. Here, $A$ is the matrix, v is the eigenvector, and $\lambda$ is the eigenvalue. This concept is important in understanding how certain mathematical operations affect vectors.

To understand this, imagine you have a vector and you apply a matrix to it. If the direction of the vector remains the same but its length changes, then you’ve found an eigenvector and its corresponding eigenvalue.

How to Find Eigenvectors?

To find eigenvectors, you first need to find the eigenvalues. This involves a bit of calculation, specifically finding the solutions to the equation $\text{det}(A-\lambda I)=0$, where $I$ is the identity matrix. Once you have the eigenvalues, you can find the eigenvectors by solving (A−λI)v=0. This basically means finding a vector that, when multiplied by the modified matrix, results in zero.

Eigenvectors of a 2×2 Matrix

For a 2×2 matrix, the process is quite straightforward. You first solve for the eigenvalues and then plug these values into (A−λI)v=0 to find the eigenvectors. The calculations are simple and involve basic algebraic steps.

Eigenvectors of a 3×3 Matrix

For a 3×3 matrix, the method is the same, but the calculations become a bit more involved. You still need to find the eigenvalues first and then determine the eigenvectors for each eigenvalue. This might require solving a system of equations but it’s nothing too complex.

Properties of Eigenvectors

Eigenvectors have several key properties:

1. Different eigenvalues have independent eigenvectors.
2. If you multiply an eigenvector by a number, it remains an eigenvector for the same eigenvalue.
3. All eigenvectors of a matrix, together with the zero vector, form a specific set known as a vector space.

Applications of Eigenvectors

Eigenvectors find use in many areas like physics, engineering, and data analysis. They help in understanding systems of equations, in studying the behavior of physical systems, and in techniques like Principal Component Analysis used in statistics.

Practice Questions on Eigenvectors

1. What is the eigenvector for the matrix:
   [3 0]
   [0 3​], corresponding to the eigenvalue 3?
2. For the matrix
   [1 2]
   [2​ 4​], what are the eigenvectors?

FAQs on Eigenvectors

Can a matrix have more eigenvectors than its size?

A matrix can have up to as many linearly independent eigenvectors as its size.

Are eigenvectors always real numbers?

Eigenvectors can be either real or complex numbers, depending on the matrix.

Is zero an eigenvector?

The zero vector is not considered an eigenvector because eigenvectors are defined to be non-zero.

Are eigenvectors used in solving linear systems?

Eigenvectors can provide insights in certain types of linear systems, although they are not always necessary for solving them.

Jo-ann Caballes

5 articles

As a seasoned educator with a Bachelor’s in Secondary Education and over three years of experience, I specialize in making mathematics accessible to students of all backgrounds through Brighterly. My expertise extends beyond teaching; I blog about innovative educational strategies and have a keen interest in child psychology and curriculum development. My approach is shaped by a belief in practical, real-life application of math, making learning both impactful and enjoyable.