# Cases equation problem - ! Missing { inserted [closed]

I am trying to compile this equation

\beta\_t^i=
\begin{cases}
\overline{\beta}-i\cdot\sigma\_{\beta} & 0\leq i\leq 4\\
0.0 & 5\leq i\leq7
\end{cases}


and I am still getting error

! Missing { inserted.


Old topics didn't help me, I think it will be problem with \\ or & but can't solve it.

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Welcome to TeX.sx! Your code snippet works fine here, when I put it within a complete document. Can you please create a minimal working example (MWE) that demonstrates the issue. This works: \documentclass{article} \usepackage{amsmath} \begin{document} $$\beta\_t^i=\begin{cases}\overline{\beta}-i\cdot\sigma\_{\beta} & 0\leq i\leq 4\\0.0 & 5\leq i\leq7\end{cases}$$ \end{document} –  Torbjørn T. Apr 28 '13 at 13:03
Thanks a lot, i didn't include amsmath, that was the problem. By the way, can including amsmath cause any visual changes to my previous equations or i shouldn't be worried? I have more than 50 of them in that document already. –  user2306381 Apr 28 '13 at 13:07
I don't think that you need to worry, probably very small differences, if any. You could always ask a separate question about just that. –  Torbjørn T. Apr 28 '13 at 13:12