Positioning formulas in latex

Question

I'm a mechanical engineer who's been doing her calculation reports in Word. However, ever since I knocked down my bedroom wall with my head banging on it from Word constantly driving me crazy, I've been looking at latex, and liking it. It is relatively user friendly and not too hard to get accustomed to.

However, I have a problem with it. Just to mention, distribution is miktex 2.7 on winxp, if that matters.

I'm trying to write my formulas in a way:

text text text text text text text text text text text text  
text text text text text text text text text text text text
a = b + c = 12m    measure of length of great importance  
   b = 6m          a measure of length  
   b1 = 28m        new text
   c1 + d = a + b  new text
   c = 8m          another measure of length  
                   and it is in meters

What would be the correct way to nicely justify these in this manner ? Is it possible at all ? I have a many of these (2 cm book thickness).

I'm a newbie concerning tex, so maybe this sounds trivial to you. But to me, after googling, it is still a problem. Please help. Save a wall.

EDIT by me: Just thought I'd explain a little better (although you guys already covered almost all the posibilities). I'm trying to left align b and c (the rest of the formula will vary, so it doesn't matter) and the text which explain the formulas, also left align.

Answer 1

Yes, justification is a common case, and supported well in LaTeX. You want to use an align environment (\begin{align} ... \end{align}). Within that, each line of LaTeX (separated with \) will correspond to one formula, and you can choose which character you would like to have aligned on each line by placing an ampersand (&). In your example:

\begin{align}
a = b + c &= 12m\\
b &= 6m\\
c &= 8m\\
\end{align}

Should do something like what you're after (depending on how you want to justify the first line). This will number each equation for reference in the text; if this is not required or desired, use an align* environment instead. Adding a star after the environment name is a common idiom in LaTeX which means "don't number these," and can be used for sections and so forth as well.

EDIT: Here's another interpretation of the justification I think you want:

text text text text text text text text text text text text  
text text text text text text text text text text text text
\begin{align*}
a = &b + c = 12m &\text{measure of length of great importance}\\  
&b = 6m &\text{a measure of length}\\
&c = 8m &\text{another measure of length}\\ 
& &\text{and it is in meters}
\end{align*}

Note:

• You can place multiple ampersands per line to specify multiple alignment points, but all lines must have the same number of alignment points.
• align is a math environment.
• \text{...} lets you put normal text in a math environment. There are many other commands to format text within a math environment.

Answer 2

I won't attempt to address your question directly since it seems to have been addressed above. I will however suggest that you try LyX to ease yourself into the TeX world. It presents a graphical interface with immediate preview that may be more intuitive given your background using word and so on. It's built upon a LaTeX base, so you're using LaTeX commands where applicable, but it's still (in my opinion), a much easier introduction to TeX.

LyX

Answer 3

You may be the first person I've ever heard describe LaTeX as "user-friendly" ;-)

Anyway, it's not entirely clear whether you're trying to align specific parts of equations or just center them. There are different equation environments for different kinds of alignment, for instance the gather environment which centers each equation on its own line.

Side note: I'd recommend looking at the Not So Short Introduction to LaTeX2e, which is how I started learning LaTeX, and the User's Guide to the amsmath Package, which describes the different kinds of alignment available.

Answer 4

I would recommend abstracting away from align and using this:

\begin{tabular}{rcll}
$a$ & $=$ & $12m$ & measure of length of great importance \\
$b$ & $=$ & $6m$  & a measure of length \\
\end{tabular}

Answer 5

You could use the standard eqnarray environment, or look at the more powerful tools available in the amsmath package.

---

If using eqnarray, you would put at least on positions anchor between the work and the text like this

\begin{eqnarray}
a = b + c = 12m  & & \mbox{measure of length of great importance}\\
   b = 6m        & & \mbox{a measure of length}\nonumber\\
...
\end{eqnarray}

lines are numbered by default, but \nonumber will suppress that. To prevent any line numbers use eqnarray* instead.

---

If you insist, you could use tables as well, but I don't recommend it. If you do, keep the whole formula in a single cell like:

\begin{tabular}{cl}
    $a = b + c = 12m$  & \mbox{measure of length of great importance}\\
    $b = 6m$           & \mbox{a measure of length}\\
 ...
\end{tabular}

this makes numbering hard.