1

Don't understand why there is some extra equation number which is coming in the last line of the equation

 \begin{subequations}
    \label{eq: non dimensional lagrangian}
     \begin{align}
     \mathcal{L}&=\mathcal{T}-\mathcal{V} \nonumber \\
       \mathcal{V}&=\frac{EI_{zz}}{2L}\, \int_{0}^{1} \hspace{-0.05in} \left(\frac{\partial^2\psi(\eta)}{\partial \eta^2}\right)^2 \mathrm{d}\eta +\frac{L^2}{2}\sum_{j=1}^{n}\,k_{1,j}\left(\psi(\eta)\right)^2 \nonumber\\
        \mathcal{T}&=\frac{\rho A\omega^2L^3}{2}\, \int_{0}^{1}  \hspace{-0.05in} \left( \psi(\eta)\right)^2 \mathrm{d}\eta \nonumber \\
        \begin{split}
     \mathcal{\bar{L}}&=\frac{\beta^4}{2}\, \int_{0}^{1}  \hspace{-0.05in} \left( \psi(\eta)\right)^2 \mathrm{d}\eta-\frac{1}{2}\, \int_{0}^{1} \hspace{-0.05in} \left(\frac{\partial^2\psi(\eta)}{\partial \eta^2}\right)^2 \mathrm{d}\eta\\ &\quad{}-\frac{1}{2}\sum_{j=1}^{n}\,K_{1,j}\left(\psi(\eta)\right)^2    
     \end{split}\\ \nonumber \\
     \end{align}
     \end{subequations}
  • 2
    Remove the last \\ – egreg Jul 23 at 10:33
  • and how to bring the equation number to the last line, now it is on somewhat upper – vijay Jul 23 at 10:40
  • Don't use split. – egreg Jul 23 at 10:42
3

You have wrong \\ in your input.

If you want the number to sit next to the last line, don't use split:

\documentclass[twocolumn]{article}
\usepackage{amsmath}

\newcommand{\diff}{\mathop{}\!\mathrm{d}}

\begin{document}

\begin{subequations}\label{eq: non dimensional lagrangian}
\begin{align}
\mathcal{L} &= \mathcal{T}-\mathcal{V} \nonumber \\
\mathcal{V} &= \frac{EI_{zz}}{2L} \int_{0}^{1} \left(
                 \frac{\partial^2\psi(\eta)}{\partial \eta^2}
               \right)^2 \diff\eta +
               \frac{L^2}{2}\sum_{j=1}^{n} k_{1,j}(\psi(\eta))^2 \nonumber \\
\mathcal{T} &= \frac{\rho A\omega^2L^3}{2} \int_{0}^{1} (\psi(\eta))^2 \diff\eta \nonumber \\
\bar{\mathcal{L}} &= \frac{\beta^4}{2} \int_{0}^{1} (\psi(\eta))^2 \diff\eta -
                     \frac{1}{2} \int_{0}^{1} \left(
                       \frac{\partial^2\psi(\eta)}{\partial \eta^2}
                     \right)^2 \diff\eta \nonumber \\
                  &\quad-\frac{1}{2}\sum_{j=1}^{n}K_{1,j}(\psi(\eta))^2    
\end{align}
\end{subequations}

\end{document}

I've made some changes to your input, in particular removing useless \left and \right. Also \mathcal{\bar{L}}, while yielding the expected result, should be \bar{\mathcal{L}} which is sounder on a logical basis.

Use \diff instead of explicit \mathrm{d} (there are many reasons to). I removed the explicit spacings you used.

enter image description here

You may find split more logical and I can agree. In this case, add the tbtags option when calling amsmath and all numbers will be aligned with the bottom line in splits.

  • 1
    Within align, I would find it more logical to nest aligned. I've forgotten where the equation number is placed by default. – barbara beeton Jul 23 at 17:00

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