8 Eigenvalues And Eigenvectors

Numerical Methods · Unit 8

Eigenvalues and Eigenvectors

Exam-focused notes for Eigenvalues and Eigenvectors (Numerical Methods, BIT203): what the TU syllabus asks and how it has actually been tested, with 4 solved past questions from this unit.

What this unit covers

  • Eigenvalue and eigenvector definitions
  • Characteristic equation and determinant method
  • Computing eigenvalues and eigenvectors
  • Applications of eigenvalue problems

Eigenvalue and eigenvector definitions

20825 marks

Define eigenvalue and eigenvector. Distinguish between regression and interpolation. [2.5+2.5]

--- (a) Eigenvalue and Eigenvector Let $A$ be an $n \times n$ square matrix. A scalar $\lambda$ is called an eigenvalue of $A$ if there exists a non-zero vector $\mathbf{x}$ such that: $$A\mathbf{x} = \lambda\mathbf{x}$$ The non-zero vector $\mathbf{x}$ sat...

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20795 marks

Define eigen value and eigen vector. Explain how shooting method is used to solve boundary value problem. [5]

--- Definition: Let $A$ be an $n \times n$ square matrix. A scalar $\lambda$ is called an eigenvalue of $A$ if there exists a non-zero vector $\mathbf{x}$ such that: $$A\mathbf{x} = \lambda \mathbf{x}$$ The non-zero vector $\mathbf{x}$ satisfying this equat...

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Computing eigenvalues and eigenvectors

20805 marks

Find the Eigen values and Eigen vectors of the Matrix: $A=\begin{bmatrix} 3 & -1 \ 1 & 1 \end{bmatrix}$ [5]

Matrix: $$A = \begin{bmatrix} 3 & -1 \\ 1 & 1 \end{bmatrix}$$ Required: eigenvalues and eigenvectors. $$\det(A - \lambda I) = 0$$ $$A - \lambda I = \begin{bmatrix} 3-\lambda & -1 \\ 1 & 1-\lambda \end{bmatrix}$$ $$\det(A - \lambda I) = (3-\lambda)(1-\lambda...

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20785 marks

Determine the Eigen Values and corresponding Eigen Vectors for the matrix.

$$A = \begin{bmatrix} 1 & 6 & 1 \ 1 & 2 & 0 \ 0 & 0 & 3 \end{bmatrix}$$

[5]

$$A = \begin{bmatrix} 1 & 6 & 1 \\ 1 & 2 & 0 \\ 0 & 0 & 3 \end{bmatrix}$$ --- $$\det(A - \lambda I) = 0$$ $$A - \lambda I = \begin{bmatrix} 1-\lambda & 6 & 1 \\ 1 & 2-\lambda & 0 \\ 0 & 0 & 3-\lambda \end{bmatrix}$$ Expand along Row 3 (only one nonzero entr...

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