Rotation around an axis
Let
- Write the matrix for
with respect to the standard basis . - Write the matrix for
with respect to the basis . - Determine all (complex) eigenvalues of
. - Is
diagonalizable over ? Justify your answer.
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Let $T:{\bf R}^3\to {\bf R}^3$ be the linear transformation that rotates counterclockwise around the $z$-axis by $\frac{2\pi}{3}$.
\begin{enumerate}[label=\alph*)]
\item Write the matrix for $T$ with respect to the standard basis $\left\{\begin{bmatrix} 1 \\ 0 \\ 0 \end{bmatrix},\begin{bmatrix} 0 \\ 1 \\ 0\end{bmatrix},\begin{bmatrix} 0 \\ 0 \\ 1\end{bmatrix}\right\}$.
\item Write the matrix for $T$ with respect to the basis $\left\{\begin{bmatrix} \frac{\sqrt{3}}{2} \\ -\frac{1}{2} \\ 0 \end{bmatrix},\begin{bmatrix} 0 \\ 1 \\ 0\end{bmatrix},\begin{bmatrix} 0 \\ 0 \\ 1\end{bmatrix}\right\}$.
\item Determine all (complex) eigenvalues of $T$.
\item Is $T$ diagonalizable over ${\bf C}$? Justify your answer.
\end{enumerate}