# man(1) Manual page archive

```delim \$\$

NAME
eqn  -  typeset mathematics

SYNOPSIS
eqn [ file ] ...

DESCRIPTION
Eqn is a troff (I) preprocessor for typesetting mathematics
on the Graphics Systems phototypesetter.  Usage is almost
always

eqn file ... | troff

If no files are specified, eqn reads from the standard
input.  A line beginning with ``.EQ'' marks the start of an
equation; the end of an equation is marked by a line begin-
ning with ``.EN''.  Neither of these lines is altered or
defined by eqn, so you can define them yourself to get cen-
tering, numbering, etc.  All other lines are treated as com-
ments, and passed through untouched.

Spaces, tabs, newlines, braces, double quotes, tilde and
circumflex are the only delimiters.  Braces ``{}'' are used
for grouping.  Use tildes ``~'' to get extra spaces in an
equation.

Subscripts and superscripts are produced with the keywords
sub and sup.  Thus x sub i makes \$x sub i\$, a sub i sup 2
produces \$a sub i sup 2\$, and e sup {x sup 2 + y sup 2}
gives \$e sup {x sup 2 + y sup 2}\$.  Fractions are made with
over.  a over b is \$a over b\$ and 1 over sqrt {ax sup 2
+bx+c} is \$1 over sqrt {ax sup 2 +bx+c}\$ .  sqrt makes
square roots.

The keywords from and to introduce lower and upper limits on
arbitrary things: \$lim from {n-> inf} sum from 0 to n x sub
i\$ is made with lim from {n-> inf}      sum from 0 to n x sub i.
Left and right brackets, braces, etc., of the right height
are made with left and right: left [ x sup 2 + y sup 2 over
alpha right ] ~=~1 produces \$left [ x sup 2 + y sup 2 over
alpha right ] ~=~1\$.  The right clause is optional.

Vertical piles of things are made with pile, lpile, cpile,
and rpile: pile {a above b above c} produces \$pile {a above
b above c}\$.  There can be an arbitrary number of elements
in a pile.  lpile left-justifies, pile and cpile center,
with different vertical spacing, and rpile right justifies.

Diacritical marks are made with dot, dotdot, hat, bar: x dot
= f(t) bar is \$x dot = f(t) bar\$.  Default sizes and fonts
can be changed with size n and various of roman, italic, and
bold.

Keywords like sum ( sum ) int ( int ) inf ( inf ) and short-
hands like >= (>=)   -> (->), != ( != ), are   recognized.
Spell out Greek letters in the desired case, as in alpha,
GAMMA.  Mathematical words like sin, cos, log are made Roman
automatically.  Troff (I) four-character escapes like \(bs

1

() can be used anywhere.  Strings enclosed in double quotes
"..."  are passed through untouched.

A System for Typesetting Mathematics (Computer Science Tech-
nical Report #17, Bell Laboratories, 1974.)
TROFF Users' Manual (internal memorandum)