4.3BSD-Tahoe/usr/lib/learn/eqn/L1.1b

#print
Most technical papers and memos consist of normal text
interspersed with occasional (or frequent) mathematical
expressions, such as the ones in the last lesson.
To tell neqn that something is mathematics, not normal
text, you must surround it by two "commands":

   A line that begins with
   .EQ
   marks the start of an expression.

   A line that begins with
   .EN
   marks the end of the expression.

Thus, the lines
.EQ
x=y+1
.EN
represent the equation

x=y+1

The file "Example" in this directory has a line that contains
+ and - signs.  Make that line into an equation
by adding .EQ and .EN before and after.
Print "Example" with neqn and nroff (and the appropriate -Txxx),
then type "ready".
#once #create Ref
This is a tiny little text
that includes one equation
or at least it will when you find this line:
.ce
.EQ
a = b + c - d
.EN
and convert it into an equation.
.pl 1
#once #create Example
This is a tiny little text
that includes one equation
or at least it will when you find this line:
.ce
a = b + c - d
and convert it into an equation.
.pl 1
#user
#cmp Ref Example
#log
#next
1.1c 10