Why does this error keep popping up even though I clearly fixed it?

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 }. - 1 Answer 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}


-
Thanks, but why doesn't TeX POINT that out? Instead of giving me misleading errors? –  Hawk May 13 '12 at 17:28
Wait why don't a need \left and \right? –  Hawk May 13 '12 at 17:28
@jak To your first question: when you get the error message, type h; then you'll get the message "I've inserted something that you may have forgotten. (See the <inserted text> above.) With luck, this will get me unwedged. But if you really didn't forget anything, try typing 2' now; then my insertion and my current dilemma will both disappear." Now type 2 and you'll get <recently read> \$. So, in fact, TeX sees the problem ;-) (not as quickly as you've expected, but it sees it). –  Gonzalo Medina May 13 '12 at 17:33
@jak to your second question: in this particular case there's no need for stretchable delimiters since the involved inner expressions do not extend vertically beyond the standard characters height. –  Gonzalo Medina May 13 '12 at 17:35
@above what that does that mean lol? stretchable delimiters...? So when do I need it? –  Hawk May 13 '12 at 17:36