Bold text and newlines inside equations.

What I'm doing:

\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{eucal}
\usepackage{amssymb}
\usepackage{mathrsfs}

% don't know what some of those do, but i think all the math related ones are
% there
% there are more packages being imported though


Then I try:

\textbf{w_{n+1}} = \textbf{w_{n}} + e\eta\textbf{x}(n) \\
\textbf{\Delta}\textbf{w} = e\eta\textbf{x}

% above doesn't work, complains about missing $\textbf{$w_{n+1}$} = \textbf{$w_{n}$} + e\eta\textbf{$x$}(n) \\ \textbf{$\Delta$}\textbf{$w$} = e\eta\textbf{$x} % above compiles, but no bold and no newline  - 4 Answers You could bold an equation with \boldsymbol. Use \align for multiline equation with alignment. \begin{align} \boldsymbol{w_{n+1}} &= \boldsymbol{w_n} + e\eta\boldsymbol{x}(n) \\ \boldsymbol{\Delta w} &= e\eta\boldsymbol{x} \end{align}  - Tried both \boldsymbol and \boldmath and neither worked. Without the it compiles, but then the text isn't bold. And with the it doesn't compile. – bada Aug 8 '10 at 7:10 @bada: Try to \usepackage{amsbsy} — although amsmath already loaded it. – kennytm Aug 8 '10 at 7:21 I added a \begin{split} after the \begin{align} and an \end{split} before the \end{align} and it worked the way I wanted. – bada Aug 8 '10 at 7:32 try $$\mathbf{A}$$ inside math environment or \boldmath$$A$$ before it – Crowley Aug 9 '10 at 7:19 \textbf is for text mode, not math mode. Also, inline math ( ... ) is for use inline, and so does not produce new lines. This is pretty basic math stuff for TeX: perhaps you should read something like Math Mode by Herbert Voss (type texdoc mathmode at the Terminal/Command Line). I think you would be best using the align environment: \documentclass{article} \usepackage{amsmath} \begin{document} \begin{align} \mathbf{w_{n+1}} &= \mathbf{w_{n}} + e\eta\mathbf{x}(n) \\ \mathbf{\Delta w} &= e\eta\mathbf{x} \end{align} \end{document}  - I'm getting a black square instead of \Delta when I use that. With \delta it's fine though. Do you know how I could fix it? Also, this gives the second line an equation number of its own, which isn't what I need. ;/ – bada Aug 8 '10 at 7:18 \usepackage{bm} \bmdefine\bDelta{\Delta} And then use \bDelta to get a bold \Delta – Martin Heller Aug 8 '10 at 11:40 Use \mathbf{w_{n+1}}$. However, if you want bold symbols, you'd have to use $\pmb{\eta}\$

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It is unfortunate that the comment of Crowley here above is not more highlighted. He give me the answer I search : using \boldmath before the eqn environment, all the math portion is in bold font and the text stay normal.

An example of my code:

   \boldmath\begin{align*}
p(X,Y) \Leftrightarrow
& minimal(X) \\
& \qquad \wedge directly-solve(X,Y) &&\mbox{ (cas de base)}\\
& \vee \\
& \neg minimal(X) \\
& \qquad \wedge decompose(X,partX,restX) &&\mbox{ (diviser)}\\
& \qquad \wedge process(partX,part-Y) &&\mbox{ (traitement interne)}\\
& \qquad \wedge p(restX,restY) &&\mbox{ (appel récursif)}\\
& \qquad \wedge compose(partY,restY,Y) &&\mbox{ (recomposer)}\\
\end{align*}


Thanks

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