Where is the full definition of the equation environment? I cannot find it in the .cls files. Is this in latex.ltx? Or something?
[Tex/LaTex] Equation environment definition
environmentsequationslatex-base
Related Solutions
You can set this in an align and use \notag to remove any equation numbers for equations you don't need numbered:
\documentclass{article}
\usepackage{mathtools}
\begin{document}
Original equation
\begin{equation}
\begin{gathered}[t]
\frac{1}{d^2} = \frac{1}{V^2} (S_{11}h^2 + S_{22} k^2 + S_{33} \ell^2 + 2S_{12}hk + 2S_{23}k\ell + 2S_{13}h\ell)\\~\\
\text{where}\\~\\
V = abc \sqrt{1 - cos^2(\alpha) - cos^2(\beta) - cost^2(\gamma) + 2cos(\alpha) cos(\beta) cos(\gamma)}\\
S_{11} = b^2c^2sin^2(\alpha)\\
S_{22} = a^2c^2sin^2(\beta)\\
S_{33} = a^2 b^2 sin^2 (\gamma)\\
S_{12} = abc^2 (cos(\alpha) cos(\beta) - cos(\gamma))\\
S_{23} = a^2bc (cos(\beta) cos(\gamma) - cos(\alpha)\\
S_{13} = ab^2c (cos(\gamma) cos(\alpha) - cos(\beta)\\
\end{gathered}
\end{equation}
Proposed improvement
\begin{align}
\frac{1}{d^2} &= \frac{1}{V^2} \bigl( S_{11}h^2 + S_{22} k^2 + S_{33} \ell^2 + 2S_{12}hk + 2S_{23}k\ell + 2S_{13}h\ell \bigr) \\
\shortintertext{where}
V &= a b c \sqrt{1 - \cos^2(\alpha) - \cos^2(\beta) - \cos^2(\gamma) + 2 \cos(\alpha) \cos(\beta) \cos(\gamma)} \notag \\
S_{11} &= b^2 c^2 \sin^2(\alpha) \notag \\
S_{22} &= a^2 c^2 \sin^2(\beta) \notag \\
S_{33} &= a^2 b^2 \sin^2 (\gamma) \notag \\
S_{12} &= a b c^2 \bigl( \cos(\alpha) \cos(\beta) - \cos(\gamma) \bigr) \notag \\
S_{23} &= a^2 b c \bigl( \cos(\beta) \cos(\gamma) - \cos(\alpha) \bigr) \notag \\
S_{13} &= a b^2 c \bigl( \cos(\gamma) \cos(\alpha) - \cos(\beta) \bigr) \notag
\end{align}
\end{document}
Best Answer
In
texdoc source2eit starts on p214. It's in ltmath.dtx.Here it is: