The set of all values of \( t\in \) ℝ for which the matrix
$\left\{ (2k+1)\frac{\pi}{2}, k \in \mathbb{Z} \right\}$
\( t\in \mathbb{R} \)
\( \{k\pi,\, k\in \ \mathbb{Z}\) }
$\left\{ k\pi + \frac{\pi}{4}, k \in \mathbb{Z} \right\}$