Section 12, “Mathematics in Type” of the Chicago Manual of Style discusses comprehensively the ins and outs of setting equations in printed materials. See also the Tools of the Trade chapter for more information.
Variable names are always set in italic.
\[x^1, y_2, z^x\]
Variable names should be as short as possible. Long variable names are difficult to typeset and make the equation more difficult to understand.
Equations should be set using the equation editor (Insert > Equation), which will ensure they are the correct font. Alternatively, the editors will do it for you, but you need to allow additional editing time.
Equations should appear on their own line and be centred.
Any symbol in an equation that is not a common mathematical sign or symbol must be defined after the equation. This is typically done with a simple “where” clause following the equation.
Knowing the tank diameter, one can determine minimum transaction or test volume as follows:
\[V \ge a \times d^2\]
where V is the test fluid volume or delivery point batch volume, d is the tank diameter, and a is the accuracy coefficient.
A tabular approach is also acceptable if the explanations are lengthy or there are a lot of variables:
The following equation is preferred because the resulting uncertainty is generally lower:
\[M = V \times \phi_{CH4} \times \rho_{CH4}\]
M the mass of methane V the volume of gas, corrected to standard conditions ΦCH4 the volumetric concentration of methane as a fraction, or molar fraction, of vent gas ρCH4 the density of methane at standard conditions
If you wish to refer to the equation later in the text, the equation can be numbered. The equation is still centred, but a number can appear flush right in parentheses.
\[a^2 + b^2 = c^2\tag{1}\]