I wanted to know if I did this problem right or not.
$A$ and $B$ are the following matrices:
$A=\begin{bmatrix}2&6\\1&-3\end{bmatrix},$
$B=\begin{bmatrix}3&2\\1&0\end{bmatrix}.$
Then
$\frac{\langle A,B\rangle}{\|A\|\|B\|} =\frac{\left\langle\begin{bmatrix}2&6\\1&-3\end{bmatrix}, \begin{bmatrix}3&2\\1&0\end{bmatrix}\right\rangle}{\sqrt{\left\langle\begin{bmatrix}2&6\\1&-3\end{bmatrix},\begin{bmatrix}2&6\\1&-3\end{bmatrix}\right\rangle}\sqrt{\left\langle\begin{bmatrix}3&2\\1&0\end{bmatrix},\begin{bmatrix}3&2\\1&0\end{bmatrix}\right\rangle}}.$
I ended up getting:
$\arccos(19/184) = 84.07^\circ$