如何框定和命名一组方程式

Question

我有以下一组方程：

\begin{align*}
    T' & =kn \\
    b' & =\tau n\\
    n' & =-\tau b-kT
\end{align*}

我想把这些方程式放入一个框中，并将描述“Formule di Frenet”放在右侧中央。

换句话说，我想扩展以下结果对一个方程的有效范围：

    \begin{equation*}
        \boxed{r:\alpha(t_0)+\Braket{\alpha'(t_0)}} \qquad \emph{retta tangente alla curva $\alpha$ nel punto $\alpha(t_0)$}
    \end{equation*}

Answer 1

用于aligned团体\boxed。

\documentclass{article}
\usepackage{amsmath,braket}
\begin{document}
    \begin{equation*}
        \boxed{r:\alpha(t_0)+\Braket{\alpha'(t_0)}} 
    \qquad \emph{retta tangente alla curva $\alpha$ nel punto $\alpha(t_0)$}
    \end{equation*}

    \begin{equation*}
        \boxed{\begin{aligned}
    T' & =kn \\
    b' & =\tau n\\
    n' & =-\tau b-kT
\end{aligned}} \qquad \emph{Formule di Frenet}
    \end{equation*}
\end{document}

Answer 2

为了好玩，还有另一种可能性，改编自文档中的代码empheq，它生成一个带有标题的阴影框：

\documentclass{article}
\usepackage[svgnames]{xcolor}
\usepackage{empheq}

\colorlet{shadecolor}{FloralWhite!60}
\colorlet{titleshade}{OliveDrab!15}
\newsavebox{\mysaveboxM} % M for math
\newsavebox{\mysaveboxT} % T for text
\newcommand*\Garybox[2][Example]{%
\sbox{\mysaveboxM}{#2}%
\sbox{\mysaveboxT}{\fcolorbox{black}{titleshade}{\enspace#1\enspace}}%
\sbox{\mysaveboxM}{%
\parbox[b][\ht\mysaveboxM+.5\ht\mysaveboxT+.5\dp\mysaveboxT][b]{%
\wd\mysaveboxM}{#2}%
}%
\sbox{\mysaveboxM}{%
\fcolorbox{black}{shadecolor}{%
\makebox[\linewidth-10em]{\usebox{\mysaveboxM}}%
}%
}%
\usebox{\mysaveboxM}%
\makebox[0pt][r]{%
\makebox[\wd\mysaveboxM][c]{%
\raisebox{\ht\mysaveboxM-0.5\ht\mysaveboxT
+0.5\dp\mysaveboxT-0.5\fboxrule}{\usebox{\mysaveboxT}}%
}%
}%
}%

\begin{document}

\begin{subequations}
\begin{empheq}[box={\Garybox[Formule di Frenet]}]{align}
    T' & =kn \\
    b' & =\tau n\\
    n' & =-\tau b-kT
\end{empheq}
\end{subequations}

\end{document}