# Latex math encapsulating complex expression in bracket

Latex newbie here. I've clumsily built the following math expression in Latex

\begin{align}
&W_{i'}(\alpha) = \cdots \notag\\
&\vdots \notag\\
&W_i(\alpha) = \sum\limits_\zeta \underline{q_\zeta} \cdot \underline{\Omega(\alpha, \zeta, \hat{u}_{i}^k, \xi )} \\
&\vdots \notag\\
&W_{i''}(\alpha) = \cdots \notag
\end{align}


and would now like to append a f(n) = \left{ to the left of it.

How do I do this without rewriting the entire code in terms of an array? Thanks!

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Afterwards you will have only one equation, therefore I assume that the two tags are now longer necessary. If this is the case proceed as follows:

1. Remove all \notags
2. change align to aligned
3. Enclose everything with rest of equation.

Here the full code:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

f(n) = \left\{ \begin{aligned} &W_{i'}(\alpha) = \cdots \\ &\vdots \\ &W_i(\alpha) = \sum\limits_\zeta \underline{q_\zeta} \cdot \underline{\Omega(\alpha, \zeta, \hat{u}_{i}^k, \xi )} \\ &\qquad \qquad \quad \ \ \downarrow \qquad \qquad \uparrow \\ &\qquad \qquad \quad \ \ \beta_i^k (\zeta) \rightarrow \hat{u}_i^k(\mathbf{x}, t) \\ &\vdots \\ &W_{i''}(\alpha) = \cdots \end{aligned} \right.

\end{document}