Typesetting long andcomplicated equations

[Athel Cornish-Bowden]

I tried to ask the following question at Stack Exchange, but for some
reason (not explained) the system didn't allow me to log in, so I'm
asking it here:

I am converting a long document in Word to LaTeX. As I’m not the
primary author I have only limited freedom to revise the text and
equations — correcting obvious errors, OK, but otherwise following what
the Word file has and not changing the symbols to I would have used. It
contains some very long and complicated equations, such as the
following:

\documentclass[12pt,a4paper]{article}
\usepackage{amsmath}
\begin{document}

\begin{align}
\nonumber \mu_j^{*0} \approx \frac{T}{298.15} \cdot \mu^0_j +
\left( 1 - \frac{T}{298.15} \right) \cdot h_j^0 + \hspace*{2cm}\\
\nonumber \mathrm{switch_{H^+}} \cdot \nu_{\mathrm{H}\varepsilon j}
\cdot R \cdot T \cdot
\ln(10) \cdot \mathrm{pH}_c\hspace*{2cm}\\
\nonumber - \mathrm{switch _{Mg}}\cdot \nu_{\mathrm{Mg} \varepsilon j}
\left[
\frac{T}{298.15} \cdot \mu^0_\mathrm{Mg^{2+}} - R \cdot T \cdot
\ln{10} \cdot \mathrm{pMg}_c \right.\\
\nonumber - \left. \left( 1 - \frac{T}{298.15}
\right) \cdot h^0_\mathrm{Mg^{2+}}
\right]
\mathrm{switch}_I \cdot g_\mathrm{DH}(I,T) \cdot \hspace*{2cm}\\
\nonumber \left[
z_i^2 - \mathrm{switch_\mathrm{H^+}} \cdot \nu_{\mathrm{H} \varepsilon j} -
\mathrm{Mg} \cdot 4\cdot \nu_{\mathrm{Mg}\varepsilon j}
\right]x\hspace*{2cm}\\
\mathrm{switch_{mM}}\cdot R \cdot T \cdot \ln\left(
\frac{c^\mathrm{standard}}{c^\mathrm{physchemstandard}}
\right)\hspace*{1cm}
\end{align}

\end{document}

This produces more or less what I want: specifically, only the last
line has an equation number, and the lines are approximately centred.
However, it seems a very clunky solution and raises two questions:

1. \nonumber before every line except the last is OK, but is there a
way to get the same result with a general command without repeating
\nonumber five times.

2. Using \hspace* to centre the lines requires a lot of fiddling about
to put the right arguments. Is there a better way? (I’ve tried obvious
things like putting each line in \begin {center} …. \end{center}.)

[Dr Engelbert Buxbaum]

Post by Athel Cornish-Bowden
I tried to ask the following question at Stack Exchange, but for some
reason (not explained) the system didn't allow me to log in, so I'm
I am converting a long document in Word to LaTeX. As I?m not the
primary author I have only limited freedom to revise the text and
equations ? correcting obvious errors, OK, but otherwise following what
the Word file has and not changing the symbols to I would have used. It
contains some very long and complicated equations
1. \nonumber before every line except the last is OK, but is there a
way to get the same result with a general command without repeating
\nonumber five times.
2. Using \hspace* to centre the lines requires a lot of fiddling about

The align-environment can do much of the work for you, if you use the &
to align the beginning of each line. The equations won't be centered,
but the operation signs at the beginning of each line will align just
right of the \approx, making it clear that all lines belong to the same
equation:

\begin{align}
\nonumber \mu_j^{*0} \approx & \frac{T}{298.15} \cdot \mu^0_j + \left
( 1 - \frac{T}{298.15} \right) \cdot h_j^0 \\
\nonumber & + \mathrm{switch_{H^+}} \cdot \nu_
{\mathrm{H}\varepsilon j} \cdot R \cdot T \cdot \ln(10) \cdot \mathrm
{pH}_c \\
\nonumber & - \mathrm{switch _{Mg}}\cdot \nu_
{\mathrm{Mg} \varepsilon j} \left[ \frac{T}{298.15} \cdot \mu^0_\mathrm
{Mg^{2+}} - R \cdot T \cdot
\ln{10} \cdot \mathrm{pMg}_c \right.\\
\nonumber & - \left. \left( 1 - \frac{T}{298.15}
\right) \cdot h^0_\mathrm{Mg^{2+}}
\right] \mathrm{switch}_I \cdot g_\mathrm{DH}(I,T) \\
\nonumber & \cdot \left[z_i^2 - \mathrm{switch_
\mathrm{H^+}} \cdot \nu_{\mathrm{H} \varepsilon j} - \mathrm{Mg} \cdot 4
\cdot \nu_{\mathrm{Mg}\varepsilon j} \right]x \\
& \cdot \mathrm{switch_{mM}}\cdot R
\cdot T \cdot \ln\left( \frac{c^\mathrm{standard}}{c^\mathrm
{physchemstandard}} \right)
\end{align}

(at the beginning of the last line I added a \cdot so it, too, starts
with an operation). Optionally, you may replace all \cdot by the more
common \times.

Hope that helps
Engelbert

[Peter Flynn]

[snip]

IANAM :-) but...

Optionally, you may replace all \cdot by the more common \times.

I would definitely do that, because it makes the LH side of each line
align better. The only manual adjustment I would make is to move the
large open parenthesis at the start of line 4 slightly leftwards to
improve the optical alignment.

\nonumber&-\kern-2pt\left.\left(1-\frac{T}{298.15}\right)...

Peter