Multiline equation group ?

[J.R.St...@physics.org]

I now have the equations in about half of the pages of Chapters I & II of <http://www.ltas-vis.ulg.ac.be/cmsms/uploads/File/Lagrange_essai_3corps.pdf> expressed in MathJax.  There are several instances of multiline equation groups (e.g. on p.231), of a form roughly indicated below and better shown in a green box in a short HTML page <http://www.merlyn.demon.co.uk/one-page.htm>.  The version in <one-page.htm> uses a three-row HTML Table, in which three TD elements contain MathJax.  Is there a better way to do it? - and, if so, please give sufficient clues.  Note - below, the three left braces should be one big brace.

        {  equation 1 containing several \frac
(A)     {  equation 2 containing several \frac
        {  equation 3 containing several \frac

--
(c) John Stockton, near London, UK. Using Google, no spell-check.
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[Davide P. Cervone]

I'd recommend

\left\{

\begin{array}{l} {d^2x \over dt^2} + ( {{A+B} \over r^2} + {C \over r''^2} ) x + C ( {1 \over r'^2} - {1 \over r''^2} ) x' = 0,\\ {d^2y \over dt^2} + ( {{A+B} \over r^2} + {C \over r''^2} ) y + C ( {1 \over r'^2} - {1 \over r''^2} ) y' = 0,\\ {d^2z \over dt^2} + ( {{A+B} \over r^2} + {C \over r''^2} ) z + C ( {1 \over r'^2} - {1 \over r''^2} ) z' = 0; \end{array} \right.

for your example from one-page.html

The "\left\{" makes a stretchy brace on the left, and the "\right." makes a matching delimiter that is blank (\left and \right must come in pairs).  The "\begin{array}{l}" starts an array with one column that is left-justified, and it ends at "\end{array}".  The rows are searpated by "\\".  (If you had more than one column, the entries in a row would be separated by "&".)

See Carol Fisher's excellent list of macros and examples for more information on what macros are available in TeX and how to use them.

Davide

[Thomas Leathrum]

If you want to align the equations, use \begin{aligned}...\end{aligned}, like in this small sample:

\left\{\begin{aligned}
\frac{a}{b}&=\frac{c}{d}\\
\frac{e}{f}&=\frac{h}{i}
\end{aligned}\right.

The "&=" tells the alignment environment to align the equations at rhe "=" sign. This is equivalent to an array environment with two columns, like \begin{array}{rl}...\end{array}.

[J.R.St...@physics.org]

Thanks to Davide and to Thomas.  Both pieces of code installed and, of course, working.  I have been reading Carol Fisher's page
<http://www.onemathematicalcat.org/MathJaxDocumentation/TeXSyntax.htm>, but it has a lot to learn.