Multiple math mode lines in a row

math-mode

Is there a way to have multiple math mode lines in a row without doing anything fancy? This is what I want, shown below. There isn't any extra space and the equations all appear with normal indentation:

This was achieved using this ugly code, involving a new paragraph per equation:

Three solutions to $3x + 5y = 1$:

$t = 1: (7, -4)$

$t = 2: (12, -7)$
          
$t = -1: (12, -7)$

I saw one solution suggest the align* environment with & in front of everything, but that results in extra indentation, shown below:

I'm a bit surprised I've been stuck on this since this sounds so basic. Am I missing something obvious? Thanks for reading.

Best Answer

align is centred by default, if you want flush left displays use [fleqn] (and set \mathindent to zero)

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[Tex/LaTex] column and row vectors with builtin math mode

For the cases where you are starting and ending in different macros just split the definition of \ensuremath in to two. So put

\relax\ifmmode\let\myend\relax\else$\def\myend{$}\fi

At the start of the first macro definition and

\myend

at the end of the second one.

Note however a format such as LaTeX works best if package authors follow the syntax guidelines so that the language as a whole remains more or less coherent and consistent. TeX makes a big distinction between math mode and text mode \. is not the same as \dot for example, and a user needs to be aware if they are in math mode or text. Sometimes for some small symbols where the user may not really need to know that math mode is being used internally \ensuremath is useful, but it is not usually a good idea to use it for something like a vector taking user-supplied arguments as the user in any case needs to know that the supplied arguments are processed as math. Compare the standard LaTeX array environment, this is identical to tabular except that each cell is in math mode, however rather than make this switch to math mode implicit the environment checks that it is not already in math mode and makes an error if not. Thus the user needs to switch to math before using array. This error check is purely for maintaining language consistency, the array environment would otherwise work in the same way in text or math. Similar considerations apply to argument structure. LaTeX comamnds never take variable number of {} arguments. {} arguments are intended to be mandatory. Optional arguments should be in [] and variable number of items should be in comma separated list, so \colvec{a,b} would be a syntax far more compatible with latex than \colvec{a}{b} if the vector may be of arbitrary length.

[Tex/LaTex] Math mode align multiple lines with different number of columns

I suggested you use an aligned for the internal alignment:

\documentclass[10pt,twocolumn,letterpaper]{article}

\usepackage{amsmath}

\begin{document}

\begin{align}
  Q(c) &= \max_{k}
         \!\begin{aligned}[t]
           & \prod_{t=1}^T \cdot p(t,c|k) \\
           & \cdot z(k)
         \end{aligned}
             \nonumber\\
       &= Q(z(c)) + p(t,c|z(k))
\end{align}

\end{document}

aligned is much like align but just for internal blocks of an equation. It takes an optional argument t or b to specify its vertical placement relative to the surrounding equation. The \! kills a small space that it is automatically inserted in front of aligned.

Best Answer

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[Tex/LaTex] column and row vectors with builtin math mode

[Tex/LaTex] Math mode align multiple lines with different number of columns

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