Align

Align

[David Arnold]

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Hans,

A second example for today. This file shows the concern that members of the
AMS have for spacing around equal signs in aligned environments. Contrast
the align with the standard eqnarray from latex2e.

\documentclass{article}
\usepackage{amsmath}
\newcommand{\norm}[1]{\left\Vert#1\right\Vert}
\newcommand{\eps}{\varepsilon}
\DeclareMathOperator{\RE}{Re} \DeclareMathOperator{\IM}{Im}\begin{document}
\newcommand{\seq}[1]{\left<#1\right>}

\begin{align*}
  \norm{f_0 - (I+\eps A)f}^2
  &= \norm{f_0-f - \eps A f}^2 \\
  &= \norm{f_0-f}^2 - 2\eps\RE\seq{A{f},f_0-f} + \eps^2\norm{A{f}}^2 \\
  &< \norm{f_0-f}^2 - 2\eps\delta + \eps^2 4\norm{A}^2 \\
  &= \norm{f_0-f}^2 - 2\eps(\delta - \eps 2\norm{A}^2) \\
  &< \norm{f_0-f}^2.
\end{align*}

\begin{eqnarray*}
  \norm{f_0 - (I+\eps A)f}^2
  &=& \norm{f_0-f - \eps A f}^2 \\
  &=& \norm{f_0-f}^2 - 2\eps\RE\seq{A{f},f_0-f} + \eps^2\norm{A{f}}^2 \\
  &<& \norm{f_0-f}^2 - 2\eps\delta + \eps^2 4\norm{A}^2 \\
  &=& \norm{f_0-f}^2 - 2\eps(\delta - \eps 2\norm{A}^2) \\
  &<& \norm{f_0-f}^2.
\end{eqnarray*}

\end{document}

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Re: Align

[Taco Hoekwater]

>>>>> "David" == David Arnold <darnold@northcoast.com> writes:

    David> Hans, A second example for today. This file shows the
    David> concern that members of the AMS have for spacing around
    David> equal signs in aligned environments. Contrast the align
    David> with the standard eqnarray from latex2e.

'Standard' eqnarray is very ugly indeed.

Taco

-- 
Taco Hoekwater                                 taco.hoekwater@wkap.nl
Kluwer Academic Publishers                            -- Pre Press --
Achterom 119, 3311 KB Dordrecht, The Netherlands  tel.  31-78-6392550
---------------------------------------------------------------------

align

[David Arnold]

All,

In ams math, the default behavior of align is to align each equation on the
&. By default, each equation is numbered. Individual equations can be
labeled and referenced. Try:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{align}
F(x)&=\int_0^x f(t)\, dt\label{eq:1}\\
F'(x)&=f(x)\label{eq:2}
\end{align}

In equation~(\eqref{eq:1}) and equation~(\eqref{eq:2}), we see\ldots
\end{document}

To suppress number of equations, we use the align* environment. Try:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{align*}
F(x)&=\int_0^x f(t)\, dt\\
F'(x)&=f(x)
\end{align*}

\end{document}

When one wants to number an aligned environment as a group, we use aligned
instead of align. This requires that we be in math mode. Try:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{equation}\label{fundthm}
\begin{aligned}
F(x)&=\int_0^x f(t)\, dt\\
F'(x)&=f(x)
\end{aligned}
\end{equation}

\end{document}

I can get this with amsl, with:

\usemodule[amsl]

\starttext

\placeformula[fundthm]
\startalign
F(x)&=\int_0^x f(t)\, dt\\
F'(x)&=f(x)
\stopalign

We see in the \in{Fundamental Theorem}[fundthm] \ldots

\stoptext

I'm not sure how to label and reference individual equations in the align
environment, however.