[Tex/LaTex] Aligning the \text in formula

horizontal alignmentlyxmath-mode

I have, let's say, 5 of the equations spread throughout the document and I want them to be aligned similarly. The equation consist of two parts — the formula itself and short descriptions (let's say boundaries). Obviously, there can be a lot of text (plus figures between) between any two equations. Can all the equations (and their parts) be aligned in the same way? This is an example:

\[
G=G_{I}=\begin{cases}
\cfrac{K_{I}^{2}}{E} & \text{plane stress}\\
\cfrac{(1-\nu^{2})K_{I}^{2}}{E} & \text{plane strain}
\end{cases}
\]

img

One equations with two lines, short comment about them, the part on the right aligned in the same way. However, I can't find a solution to align these throughtout the document (i.e., in multiple equations). It should look something like this

img

but the boundaries in this case are misaligned and the & operator can't be used. Is there a feature I'm missing or a workaround?

Best Answer

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\noindent Something\dots
\begin{alignat*}{2}
  K_{C} &= \sqrt{EG_{c}} &\qquad &\text{(plane stress)}\\
  \intertext{further description of the equation}
  K_{c} &= \sqrt{\frac{EG_{c}}{1-\nu^{2}}} &&\text{(plane strain)}
\end{alignat*}
Something\dots

\end{document}

output

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