Eigenvalues and eigenvectors
Find eigenvalues of a matrix Find eigenvectors of a matrix

Find eigenvalues of a matrix

Suppose you want to know the eigenvalues of the following matrix:

\[ A = \begin{pmatrix} -2 & -24 \\ 3 & 16 \end{pmatrix} \]

  1. Create a new document and select Add Calculator.
  2. Create the matrix:
    • Press Menu Icon and select Matrix & Vector > Create > Matrix.
    • Enter the number of rows (2) and columns (2). Press Enter Icon and write the matrix values.
  3. Store the matrix and name it a: Press Control Icon and Store Icon. Write a and press Enter Icon.
  4. Compute the eigenvalues:
    • Press Menu Icon and select Matrix & Vector > Advanced > Eigenvalues.
    • Write a inside the brackets of eigVl() and press Enter Icon.

    Recursive Formula Example

    The results should be \( \lambda_1 = 4 \) and \( \lambda_2 = 10 \), which are the eigenvalues.

Find eigenvectors of a matrix

Consider the following matrix:

\[ A = \begin{pmatrix} -2 & -24 \\ 3 & 16 \end{pmatrix} \]

Suppose you want to compute the eigenvectors associated with \( \lambda_1 = 4 \) and \( \lambda_2 = 10 \).

  1. Write the homogeneous linear system associated with the eigenvalue: \[ \left( A - \lambda I \right) \begin{pmatrix} x \\ y \end{pmatrix} = \begin{pmatrix} 0 \\ 0 \end{pmatrix} \] Here: \[ \begin{cases} -6x - 24y = 0 \\ 3x + 12y = 0 \end{cases} \]
  2. Solve the system using the calculator:
    • Press Menu Icon and select Algebra > Solve System of Equations > Solve System of Linear Equations.
    • The result should display \( y \) as a free variable and \( x = -4y \).
    • Recursive Formula Example

  3. Interpret the solution:

    The eigenvectors are represented as: \[ t \begin{pmatrix} -4 \\ 1 \end{pmatrix} \] Here, \( t \) is a free variable. A possible eigenvector is: \[ x_1 = \begin{pmatrix} -4 \\ 1 \end{pmatrix} \]

  4. Repeat the process for \( \lambda_2 = 10 \). A possible eigenvector is: \[ x_2 = \begin{pmatrix} -2 \\ 1 \end{pmatrix} \]