[Tex/LaTex] Breaking formulas before and after binary operators

equationsline-breakingtypography

Page 195 of the TeXBook reads:

Although formulas within a paragraph always break after binary operations and relations, displayed formulas always break before binary operations and relations.

What is the reason for this rule?

Best Answer

That statement by Knuth regarding displayed equations is Knuth's opinion. It is not a universally accepted typography rule. From a quick glance at multiple books and journals, there apparently is not a universally accepted typography rule.

  • Some use the rule as espoused by Knuth.
  • Some use the opposite rule: displayed equations are split after a binary operator.
  • You would think that those are the only choices. They aren't. Some take a third route: Repeat the binary operator at the end of one line and at the start of the next.