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A First Course in Linear Algebra, 2017a

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7.2. Diagonalization 355<br />

One eigenvalue is −2.<br />

Exercise 7.1.13 F<strong>in</strong>d the eigenvalues and eigenvectors of the matrix<br />

⎡<br />

3 5<br />

⎤<br />

2<br />

⎣ −8 −11 −4 ⎦<br />

10 11 3<br />

One eigenvalue is -3.<br />

Exercise 7.1.14 Is it possible for a nonzero matrix to have only 0 as an eigenvalue?<br />

Exercise 7.1.15 If A is the matrix of a l<strong>in</strong>ear transformation which rotates all vectors <strong>in</strong> R 2 through 60 ◦ ,<br />

expla<strong>in</strong> why A cannot have any real eigenvalues. Is there an angle such that rotation through this angle<br />

would have a real eigenvalue? What eigenvalues would be obta<strong>in</strong>able <strong>in</strong> this way?<br />

Exercise 7.1.16 Let A be the 2 × 2 matrix of the l<strong>in</strong>ear transformation which rotates all vectors <strong>in</strong> R 2<br />

through an angle of θ. For which values of θ does A have a real eigenvalue?<br />

Exercise 7.1.17 Let T be the l<strong>in</strong>ear transformation which reflects vectors about the x axis. F<strong>in</strong>d a matrix<br />

for T and then f<strong>in</strong>d its eigenvalues and eigenvectors.<br />

Exercise 7.1.18 Let T be the l<strong>in</strong>ear transformation which rotates all vectors <strong>in</strong> R 2 counterclockwise<br />

through an angle of π/2. F<strong>in</strong>d a matrix of T and then f<strong>in</strong>d eigenvalues and eigenvectors.<br />

Exercise 7.1.19 Let T be the l<strong>in</strong>ear transformation which reflects all vectors <strong>in</strong> R 3 through the xy plane.<br />

F<strong>in</strong>d a matrix for T and then obta<strong>in</strong> its eigenvalues and eigenvectors.<br />

7.2 Diagonalization<br />

Outcomes<br />

A. Determ<strong>in</strong>e when it is possible to diagonalize a matrix.<br />

B. When possible, diagonalize a matrix.

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