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Asked: 2020-10-01 08:41:36 +0800 CST 2020-10-01 08:41:36 +0800 CST

How to reset equation number to \begin{align} in LaTeX?

  • 772

I have the following code in Overleaf:

\begin{align}
\frac{\partial\Lagr}{\partial x_{1}} &= x_{2} + 2x_{1}\lambda_{1} = 0 \\ \frac{\partial\Lagr}{\partial x_{2}} &= x_{1} + x_{3} + 2x_{2}\lambda_{1} + \lambda_{2} = 0\\
%
\frac{\partial\Lagr}{\partial x_{3}} &= x_{2} + \lambda_{2} = 0\\
%
\frac{\partial\Lagr}{\partial \lambda_{1}} &= x_{1}^2 + x_{2}^2 - 2 = 0 \\ \frac{\partial\Lagr}{\partial \lambda_{2}} &= x_{2} + x_{3} -2 = 0 
\end{align}

Which generates this:

enter image description here

Which is what I want, however, later I do another one \begin{align}in which I want the numbers of the equations to be reset, to start from 1 again, this has the following code:

\begin{align}
-2\cdot\alpha_{1} &= 0\\
2\cdot\alpha_{1} + \alpha_{2} &= 0\\
\alpha_{2} &= 0\\
\Rightarrow \alpha_{1} = \alpha_{2} &= 0
\end{align}

And this continues with the sequence of numbers: enter image description here

Which is not what I want.

There I found commands like:

  1. \newcounter{foo}[counter]
  2. \setcounter{counter}{0}

And they don't work for me, or I don't know how to use them in these sections.

latex

2 Answers

  1. Best Answer

    The command to reset a counter is \setcounter{contador}{0}. The trick is knowing what the counter you want to reset is called.

    In the case of equations, the counter is called equation, so just put the following line before the second align:

    \setcounter{equation}{0}

    Result

    • 3

  2. A different approach to the problem would be to use{subequations}

    Primer grupo

\begin{subequations}
  \begin{align}
    -2\cdot\alpha_{1} &= 0\\
    2\cdot\alpha_{1} + \alpha_{2} &= 0\\
    \alpha_{2} &= 0\\
    \Rightarrow \alpha_{1} = \alpha_{2} &= 0
  \end{align}
\end{subequations}

Segundo grupo

\begin{subequations}
  \begin{align}
    -2\cdot\alpha_{1} &= 0\\
    2\cdot\alpha_{1} + \alpha_{2} &= 0\\
    \alpha_{2} &= 0\\
    \Rightarrow \alpha_{1} = \alpha_{2} &= 0
  \end{align}
\end{subequations}

    Example:

    enter image description here

    Otherwise, and as a complement to abulafia's answer, you can use etoolboxto connect the start event of the alignand restart the counter of these automatically

    \documentclass{article}
\usepackage{amsmath}
\usepackage[utf8]{inputenc}

\usepackage{etoolbox}

\AtBeginEnvironment{align}{\setcounter{equation}{0}}

\begin{document}

Grupo 1
\begin{align}
-2\cdot\alpha_{1} &= 0\\
2\cdot\alpha_{1} + \alpha_{2} &= 0\\
\alpha_{2} &= 0\\
\Rightarrow \alpha_{1} = \alpha_{2} &= 0
\end{align}

Aquí el otro grupo, con reseteo de numeración
\begin{align}
-2\cdot\alpha_{1} &= 0\\
2\cdot\alpha_{1} + \alpha_{2} &= 0\\
\alpha_{2} &= 0\\
\Rightarrow \alpha_{1} = \alpha_{2} &= 0
\end{align}

\end{document}

    Example:

    enter image description here

    • 2