在等式下方插入名称

Question

我有这个代码

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[margin=2.5cm,showframe]{geometry}
\usepackage{amsmath}

\begin{document}

\begin{equation}
    dy_{t}
        =\frac{\partial g}{\partial t}(x_{t},t)dt
        +\frac{\partial g}{\partial x}(x_{t},t)dx_{t}
        +\frac{1}{2}\frac{\partial^2 g}{\partial x^2}(x_{t},t)(dx_{t})^2
\end{equation}

\end{document}

产生这个输出

有没有办法给这个方程起个名字，fx伊藤引理并将其直接插入到等式下方（居中）？这个想法是它仍然是\begin{equation}...\end{equation}。我读过这，但解决方案并不完全相同。提前致谢！

Answer 1

这似乎不是一个好主意，但文档是你的。然而，链接问题中的方法更糟糕。

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[margin=2.5cm,showframe]{geometry}
\usepackage{amsmath}

\begin{document}

\begin{gather}
    dy_{t}
        =\frac{\partial g}{\partial t}(x_{t},t)dt
        +\frac{\partial g}{\partial x}(x_{t},t)dx_{t}
        +\frac{1}{2}\frac{\partial^2 g}{\partial x^2}(x_{t},t)(dx_{t})^2
\\
\text{Itô's lemma}\notag
\end{gather}

\end{document}

为了完整起见，我宁愿选择下面这样的内容。

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[margin=2.5cm,showframe]{geometry}
\usepackage{amsmath}

\begin{document}

We obtain the following equation, known as \emph{Itô's lemma},
\begin{equation}
    dy_{t}
        =\frac{\partial g}{\partial t}(x_{t},t)dt
        +\frac{\partial g}{\partial x}(x_{t},t)dx_{t}
        +\frac{1}{2}\frac{\partial^2 g}{\partial x^2}(x_{t},t)(dx_{t})^2
\end{equation}

\end{document}

如果您遇到这种情况，我可以提出类似的建议。

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[margin=2.5cm,showframe]{geometry}
\usepackage{amsmath}
\usepackage{nccmath}

\begin{document}

\section{Main body}

We recall the fundamental \emph{Pythagoras' theorem}
\begin{equation}\label{pyth}
a^2+b^2=c^2
\end{equation}
From it we easily obtain the following equation, known as \emph{Itô's lemma},
\begin{equation}\label{ito}
    dy_{t}
        =\frac{\partial g}{\partial t}(x_{t},t)dt
        +\frac{\partial g}{\partial x}(x_{t},t)dx_{t}
        +\frac{1}{2}\frac{\partial^2 g}{\partial x^2}(x_{t},t)(dx_{t})^2
\end{equation}

\begin{fleqn}[2em]
\setlength{\parindent}{0pt}

\section{Equations}

Pythagoras' theorem
\begin{equation}\tag{\ref{pyth}}
a^2+b^2=c^2
\end{equation}

Itô's lemma
\begin{equation}\tag{\ref{ito}}
    dy_{t}
        =\frac{\partial g}{\partial t}(x_{t},t)dt
        +\frac{\partial g}{\partial x}(x_{t},t)dx_{t}
        +\frac{1}{2}\frac{\partial^2 g}{\partial x^2}(x_{t},t)(dx_{t})^2
\end{equation}

\end{fleqn}

\end{document}

或者，在名称旁边加上引用：

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[margin=2.5cm,showframe]{geometry}
\usepackage{amsmath}
\usepackage{nccmath}

\begin{document}

\section{Main body}

We recall the fundamental \emph{Pythagoras' theorem}
\begin{equation}\label{pyth}
a^2+b^2=c^2
\end{equation}
From it we easily obtain the following equation, known as \emph{Itô's lemma},
\begin{equation}\label{ito}
    dy_{t}
        =\frac{\partial g}{\partial t}(x_{t},t)dt
        +\frac{\partial g}{\partial x}(x_{t},t)dx_{t}
        +\frac{1}{2}\frac{\partial^2 g}{\partial x^2}(x_{t},t)(dx_{t})^2
\end{equation}

\begin{fleqn}[2em]
\setlength{\parindent}{0pt}

\section{Equations}

Pythagoras' theorem~\eqref{pyth}
\begin{equation*}
a^2+b^2=c^2
\end{equation*}

Itô's lemma~\eqref{ito}
\begin{equation*}
    dy_{t}
        =\frac{\partial g}{\partial t}(x_{t},t)dt
        +\frac{\partial g}{\partial x}(x_{t},t)dx_{t}
        +\frac{1}{2}\frac{\partial^2 g}{\partial x^2}(x_{t},t)(dx_{t})^2
\end{equation*}

\end{fleqn}

\end{document}