Multiline equations

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Basic Alignment

Two modes of input

• Latex style

\startformula \startalign
 v &= u + at \\
 h &= ut + \frac12 gt^2 \\
\stopalign \stopformula

Note the \\ in the last line, above.

This appears as follows:

• Context Style

\startformula \startalign
 \NC v \NC = u + at \NR
 \NC h \NC= ut + \frac12 gt^2 \NR
\stopalign \stopformula

(The examples here will focus on the context style, having two styles can be confusing -- Aditya )

Changing the number of columns

The above equations were aligned at =. Suppose you also want the + to align. Well, this is simple in context, simply specify the number of columns with \startalign

\startformula \startalign[n=3]
 \NC v \NC = u \NC+ at \NR
 \NC h \NC= ut \NC+ \frac12 gt^2 \NR
\stopalign \stopformula

Alignment of each column

If you want more control over the formatting, and want the middle column to be center aligned, you can do that by

\startformula \startalign[n=3,align={right,middle,left}]
 \NC v \NC = u \NC+ at \NR
 \NC h \NC= ut \NC+ \frac12 gt^2 \NR
\stopalign \stopformula

This mechanism allows fancier alignments like

\startformula \startalign[n=4,align={left,right,middle,left}]
 \NC \text{We have} \quad \NC v \NC = u \NC+ at \NR
 \NC \text{and}           \NC h \NC= ut \NC+ \frac12 gt^2 \NR
\stopalign \stopformula

Working with equation numbering

aligned equations can be numbered by placing a tag after \NR

\placeformula \startformula \startalign
 \NC v \NC = u + at \NR[eq:v]
 \NC h \NC = ut + \frac12 gt^2 \NR[eq:h]
\stopalign \stopformula
Equation (\in[eq:v]) tells the final velocity after 
time $t$ and equation (\in[eq:h]) tells the distance 
travelled in time $t$.

Defining new alignment structures

New alignment can be defined using \definemathalignment. For example, to emulate gather environment of amsmath, we can use

\definemathalignment
    [gather]
    [n=1,align={middle}]

\startformula \startgather
 \NC  ax^2 + bx + c = 0 \NR
 \NC \text{roots} = \frac{ -b \pm \sqrt{b^2 - 4ac}}{2a} \NR
\stopgather \stopformula

Cases

Context provides a \startmathcases \stopmathcases pair to make it easy get cases.

\startformula
 f(x) = \startmathcases
   \NC x, \NC if $0 \le x \le \frac12$ \NR
   \NC 1-x ,\NC if $\frac12 \le x \le 1$ \NR
\stopmathcases
\stopformula

gives

The cases environment consists of two columns, separated by \NC. The second column is by default in text mode. Each line must end with a \NR.