Letter symbols are set in italic (see rule 10.8) or in roman (see rule 9.56) without periods and are capitalized only if so shown in copy, since the capitalized form may have an entirely different meaning.
In mathematical equations, use italic for all letter symbols—capitals, lowercase, small capitals, and superiors and inferiors (exponents and subscripts); use roman for figures, including superiors and inferiors.
If an equation or a mathematical expression needs to be divided, break before +, -, =, etc. However, the equal sign is to clear on the left of other beginning mathematical signs.
A short equation in text should not be broken at the end of a line. Space out the line so that the equation will begin on the next line; or better, center the equation on a line by itself.
An equation too long for one line is set flush left, the second half of the equation is set flush right, and the two parts are balanced as nearly as possible.
Two or more equations in a series are aligned on the equal signs and centered on the longest equation in the group.
Connecting words of explanation, such as hence, therefore, and similarly, are set flush left either on the same line with the equation or on a separate line.
Parentheses, braces, brackets, integral signs, and summation signs should be of the same height as the mathematical expressions they include.
Inferiors precede superiors if they appear together; but if either inferior or superior is too long, the two are aligned on the left.
