This is just a toot demonstrating inline math such as \(e^{i\theta} = \cos \theta + i \sin \theta\) and display math, such as

\[f(v) = Av\]

where
\[ A = \begin{pmatrix}
3 & 0 & 0 \\
0 & 2 & 0 \\
0 & 0 & \varphi
\end{pmatrix} \]