# subequations align

Can anyone help me fix this problem? Actually, there is no need to have 1(b), 1(d), 1(f) and 1(h) since they are deriving from the last line. Can I have just four subequations?

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{subequations}
\begin{alignat}{4}
E_{11}&=Q_{11}^2\ln\sqrt{B'_{11}} +Q_{12}^2\ln\sqrt{B'_{22}}+Q_{13}^2\ln\sqrt{B'_{33}}\\
&=Q_{11}^2\ln\sqrt{B'_{11}}+Q_{21}^2\ln\sqrt{B'_{33}}\\
E_{12}&=Q_{11}Q_{21}\ln\sqrt{B'_{11}}     +Q_{12}Q_{22}\ln\sqrt{B'_{22}}+Q_{13}Q_{23}\ln\sqrt{B'_{33}} \\
&=Q_{11}Q_{21}\ln\sqrt{B'_{11}}-Q_{11}Q_{21}\ln\sqrt{B'_{33}}\\
E_{22}&=Q_{21}^2\ln\sqrt{B'_{11}} +Q_{22}^2\ln\sqrt{B'_{22}}+Q_{23}^2\ln\sqrt{B'_{33}}\\
&=Q_{21}^2\ln\sqrt{B'_{11}} +Q_{11}^2\ln\sqrt{B'_{33}}\\
E_{33}&=Q_{31}^2\ln\sqrt{B'_{11}} +Q_{32}^2\ln\sqrt{B'_{22}}+Q_{33}^2\ln\sqrt{B'_{33}}\\
&=Q_{32}^2\ln\sqrt{B'_{22}}
\end{alignat}
\label{straincomponent}
\end{subequations}

\end{document}

• I prefer to put \label{straincomponent} next to \begin{subequations}, where it's more easily seen; it changes nothing in the output, of course. – egreg Mar 13 '15 at 17:24
• Please start accepting answers to mark your questions as solved. As I told you in other questions of yours, please see How do you accept an answer? – karlkoeller Mar 13 '15 at 18:34
• And how do you make reference for each individual subproblem in a text? – Christina Aug 5 '17 at 8:33

another variation, with the equation number for each pair positioned vertically between the two lines:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{subequations}
\begin{align}
\begin{split}
E_{11}&=Q_{11}^2\ln\sqrt{B'_{11}} +Q_{12}^2\ln\sqrt{B'_{22}}+Q_{13}^2\ln\sqrt{B'_{33}}\\
&=Q_{11}^2\ln\sqrt{B'_{11}}+Q_{21}^2\ln\sqrt{B'_{33}}
\end{split}\\
\begin{split}
E_{12}&=Q_{11}Q_{21}\ln\sqrt{B'_{11}}     +Q_{12}Q_{22}\ln\sqrt{B'_{22}}+Q_{13}Q_{23}\ln\sqrt{B'_{33}} \\
&=Q_{11}Q_{21}\ln\sqrt{B'_{11}}-Q_{11}Q_{21}\ln\sqrt{B'_{33}}
\end{split}\\
\begin{split}
E_{22}&=Q_{21}^2\ln\sqrt{B'_{11}} +Q_{22}^2\ln\sqrt{B'_{22}}+Q_{23}^2\ln\sqrt{B'_{33}}\\
&=Q_{21}^2\ln\sqrt{B'_{11}} +Q_{11}^2\ln\sqrt{B'_{33}}
\end{split}\\
\begin{split}
E_{33}&=Q_{31}^2\ln\sqrt{B'_{11}} +Q_{32}^2\ln\sqrt{B'_{22}}+Q_{33}^2\ln\sqrt{B'_{33}}\\
&=Q_{32}^2\ln\sqrt{B'_{22}}
\end{split}
\end{align}
\label{straincomponent}
\end{subequations}
\end{document}


Use \nonumber in the lines where you don't want a label.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{subequations}
\begin{alignat}{4}
E_{11}&=Q_{11}^2\ln\sqrt{B'_{11}} +Q_{12}^2\ln\sqrt{B'_{22}}+Q_{13}^2\ln\sqrt{B'_{33}}\\
&=Q_{11}^2\ln\sqrt{B'_{11}}+Q_{21}^2\ln\sqrt{B'_{33}}\nonumber\\
E_{12}&=Q_{11}Q_{21}\ln\sqrt{B'_{11}}     +Q_{12}Q_{22}\ln\sqrt{B'_{22}}+Q_{13}Q_{23}\ln\sqrt{B'_{33}} \\
&=Q_{11}Q_{21}\ln\sqrt{B'_{11}}-Q_{11}Q_{21}\ln\sqrt{B'_{33}}\nonumber\\
E_{22}&=Q_{21}^2\ln\sqrt{B'_{11}} +Q_{22}^2\ln\sqrt{B'_{22}}+Q_{23}^2\ln\sqrt{B'_{33}}\\
&=Q_{21}^2\ln\sqrt{B'_{11}} +Q_{11}^2\ln\sqrt{B'_{33}}\nonumber\\
E_{33}&=Q_{31}^2\ln\sqrt{B'_{11}} +Q_{32}^2\ln\sqrt{B'_{22}}+Q_{33}^2\ln\sqrt{B'_{33}}\\
&=Q_{32}^2\ln\sqrt{B'_{22}}\nonumber
\end{alignat}
\label{straincomponent}
\end{subequations}

\end{document}


• @Windy if i want to put an [and] between equation 1(a) and 1(b), what i should do. I did \text{and} but i got an error. – rudresh dwivedi May 18 '17 at 15:22
• @rudreshdwivedi --- After the double backslash, use \intertext{and}. – Ian Thompson May 18 '17 at 15:36

A variant, with a single align and 4 aligned environments. I added some vertical spacing between the groups of equations:

\documentclass{article}
\usepackage{amsmath}

\begin{document}
\begin{subequations}
\begin{align}%{4}
E_{11} & \!\begin{aligned}[t] & = Q_{11}^2\ln\sqrt{B'_{11}} +Q_{12}^2\ln\sqrt{B'_{22}}+Q_{13}^2\ln\sqrt{B'_{33}} \\
&=Q_{11}^2\ln\sqrt{B'_{11}}+Q_{21}^2\ln\sqrt{B'_{33}}
\end{aligned}\\[0.75ex]
E_{12} & \!\begin{aligned}[t] & =Q_{11}Q_{21}\ln\sqrt{B'_{11}} +Q_{12}Q_{22}\ln\sqrt{B'_{22}}+Q_{13}Q_{23}\ln\sqrt{B'_{33}} \\
& =Q_{11}Q_{21}\ln\sqrt{B'_{11}}-Q_{11}Q_{21}\ln\sqrt{B'_{33}}
\end{aligned}\\[0.75ex]
E_{22} & \!\begin{aligned}[t] & =Q_{21}^2\ln\sqrt{B'_{11}} +Q_{22}^2\ln\sqrt{B'_{22}}+Q_{23}^2\ln\sqrt{B'_{33}} \\
&=Q_{21}^2\ln\sqrt{B'_{11}} +Q_{11}^2\ln\sqrt{B'_{33}}
\end{aligned}\\[0.85ex]
E_{33} & \!\begin{aligned}[t] & =Q_{31}^2\ln\sqrt{B'_{11}} +Q_{32}^2\ln\sqrt{B'_{22}}+Q_{33}^2\ln\sqrt{B'_{33}} \\
&=Q_{32}^2\ln\sqrt{B'_{22}}
\end{aligned}
\end{align}
\label{straincomponent}
\end{subequations}

\end{document}