[Tex/LaTex] Why does this error keep popping up even though I clearly fixed it

Question

This is the code I have:

    \begin{align}
     \vec{l} \cdot \vec{n} & = \left \langle 1,2,3 \right \rangle$ \cdot \left \langle                  3,-3,1 \right \rangle \\
                           & = 3 - 6 + 3 \\
                           & = 0 \\
     \end{align}

Now for some reason, I keep getting this message:

 "Missing } inserted <inserted text> } \end{align}"

I clearly have completed my }.

Answer 1

You have \rangle$; simply delete the dollar sign. In your example, you don't really need \left and \right, so you can just say:

\documentclass{article} 
\usepackage{amsmath}

\begin{document}

\begin{align}
\vec{l} \cdot \vec{n} & = \langle 1,2,3 \rangle \cdot \langle 3,-3,1 \rangle \\
& = 3 - 6 + 3 \\
& = 0
\end{align}

\end{document}