[Tex/LaTex] Equation align two column to one column with page width

alignequations

I was trying to format the following expression using align. However, I need it in two column. Of all the equations, one is a long expression and Hence I added \rlap.

The problem is the lengthy expression is not adjusting to the page width. Could you please let me know the proper choice available?

\documentclass[]{article}
\usepackage{amsmath}
\begin{document}
\begin{align} 
 \eta_7~&=~\eta_2~f_0(\lambda)~-~\eta_1~g_0(\lambda)\nonumber&\eta_8~&=~\eta_1~f_0(\lambda)~+~\eta_2~g_0(\lambda)\nonumber\\
  \eta_9~&=~\rlap{$pEL~a~-~\displaystyle\frac{\sigma_c~\lambda^2}{2}$}&\nonumber\\
  \eta_{10}~&=~\rlap{$\sqrt{2}~\left\{4~l^2~\left[\eta_2~f_0(\lambda)~-~\eta_1~g_0(\lambda)\right]~-~\left[\lambda^2~-~a^2\right]~\left[\eta_1~f_0(\lambda)~+~\eta_2~g_0(\lambda)\right]\right\}-4~l~\lambda~\eta_6$}\nonumber
\end{align}

\begin{equation}
\eta_{10}~=~\sqrt{2}~\left\{4~l^2~\left[\eta_2~f_0(\lambda)~-~\eta1~g_0(\lambda)\right]~-~\left[\lambda^2~-~a^2\right]~\left[\eta1~f_0(\lambda)~+~\eta2~g_0(\lambda)\right]\right\}-4~l~\lambda~\eta_6\nonumber
\end{equation}
\end{document}

The equation I am having the problem is the last equation (i.e. \eta_10). The output from the align environment for \eta_10 is not spreading to the whole page width. However, the output from the equation environment is spreading to the page width.

Question: How to make the \eta_10 equation to spread to the page width. Am I missing any commands?

Best Answer

You can use flalign*:

enter image description here

Notes:

  • With the starred variant you don't need to use \nonumber.
  • I also remove the manually added ~ for spacing as manual spacing should normally be avoided in math.

Code:

\documentclass[]{article}
\usepackage{showframe}
\usepackage{amsmath}
\begin{document}
\begin{flalign*} 
 \eta_7 &= \eta_2 f_0(\lambda) - \eta_1 g_0(\lambda)\nonumber&\eta_8 &= \eta_1 f_0(\lambda) + \eta_2 g_0(\lambda)\nonumber\\
  \eta_9 &= \rlap{$pEL a - \displaystyle\frac{\sigma_c \lambda^2}{2}$}\\
  \eta_{10} &= \rlap{$\sqrt{2} \left\{4 l^2 \left[\eta_2 f_0(\lambda) - \eta_1 g_0(\lambda)\right] - \left[\lambda^2 - a^2\right] \left[\eta_1 f_0(\lambda) + \eta_2 g_0(\lambda)\right]\right\}-4 l \lambda \eta_6$}
\end{flalign*}
\end{document}
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