LaTeX forum ⇒ Math & Science ⇒ Difficulties in aligning equations under the flalign environment Topic is solved

[Cham]

I'm having some glitches with the MWE code below :

Code: [Select all] [Expand/Collapse] [Download] ({untitled.tex}) Open in Overleaf

\documentclass[12pt]{article}
\usepackage[total={6.25in,10in},left=1.25in,top=0.5in,includehead,includefoot]{geometry}
\usepackage{mathtools}
\newcommand*{\1}{\hspace{1pt}}
\newcommand*{\tsqrt}[1]{{\textstyle{\sqrt{#1}}}}
 
\begin{document}
 
Test :
	\begin{flalign}
		\mathrlap{\text{if $4 \, \omega_0^2 > \gamma^2$ :}} && \lambda &= \frac{1}{2} \1 \tsqrt{\displaystyle{4 \, \omega_0^2 - \gamma^2}}, & \\[12pt]
		\mathrlap{\text{if $4 \, \omega_0^2 < \gamma^2$ :}} && \kappa &= \frac{1}{2} \1 \tsqrt{\displaystyle{\gamma^2 - 4 \, \omega_0^2}}. &
	\end{flalign}
	\begin{equation}
		EQUATION
	\end{equation}
 
\end{document}

Here's a preview :

equs.jpg (12.45 KiB) Viewed 2971 times

As you can see, the equations aren't well centered above the "EQUATION" below them. I need them to be well balanced (i.e. centered). What am I doing wrong here?

[Johannes_B]

The equation environment does not know the content of the box (flalign) above. So the first step is to put EQUATION into the same enviroment. The example below looks ok, but you will have some real equation there and that will need extra fiddeling.
The \mathrlap stuff looks like you are used to manual spacing anyway.

Code: [Select all] [Expand/Collapse] [Download] ({untitled.tex}) Open in Overleaf

\documentclass[12pt]{article}
    \usepackage[total={6.25in,10in},left=1.25in,top=0.5in,includehead,includefoot]{geometry}
    \usepackage{mathtools}
    \newcommand*{\1}{\hspace{1pt}}
    \newcommand*{\tsqrt}[1]{{\textstyle{\sqrt{#1}}}}
 
    \begin{document}
 
    Test :
    	\begin{flalign}
    		\mathrlap{\text{if $4 \, \omega_0^2 > \gamma^2$ :}} && \lambda &= \frac{1}{2} \1 \tsqrt{\displaystyle{4 \, \omega_0^2 - \gamma^2}}, & \\[12pt]
    		\mathrlap{\text{if $4 \, \omega_0^2 < \gamma^2$ :}} && \kappa &= \frac{1}{2} \1 \tsqrt{\displaystyle{\gamma^2 - 4 \, \omega_0^2}}. & \\ 
    	&&&	EQUATION
    	\end{flalign}
 
    \end{document}

[Cham]

Johannes,

what I tried to say is that the two equations in the middle should still be centered, like "EQUATION", or if there's an "align" environment, like this :

Code: [Select all] [Expand/Collapse] [Download] ({untitled.tex}) Open in Overleaf

\documentclass[12pt]{article}
\usepackage[total={6.25in,10in},left=1.25in,top=0.5in,includehead,includefoot]{geometry}
\usepackage{mathtools}
\newcommand*{\1}{\hspace{1pt}}
\newcommand*{\tsqrt}[1]{{\textstyle{\sqrt{#1}}}}
 
\begin{document}
 
Test :
	\begin{flalign}
		\mathrlap{\text{if $4 \, \omega_0^2 > \gamma^2$ :}} && \lambda &= \frac{1}{2} \1 \tsqrt{\displaystyle{4 \, \omega_0^2 - \gamma^2}}, & \\[12pt]
		\mathrlap{\text{if $4 \, \omega_0^2 < \gamma^2$ :}} && \kappa &= \frac{1}{2} \1 \tsqrt{\displaystyle{\gamma^2 - 4 \, \omega_0^2}}. &
	\end{flalign}
	\begin{align}
		\lambda &= \frac{1}{2} \1 \tsqrt{\displaystyle{4 \, \omega_0^2 - \gamma^2}}, \\[12pt]
		\kappa &= \frac{1}{2} \1 \tsqrt{\displaystyle{\gamma^2 - 4 \, \omega_0^2}}.
	\end{align}
	\begin{equation}
		EQUATION
	\end{equation}
 
\end{document}

You should notice the offset in the middle, relative to the align and equation environments. I used the mathrlap command to try to fix this issue, but it's not enough.

[Cham]

I just noticed that the numbers are pushing the equations to the left, in the flalign environment. Why ? The same doesn't happens under the align and equation environments.

[Cham]

O well, by fizzling the equations, I fixed the alignement problem. Issue solved.

[Stefan Kottwitz]

Great to hear! Do you have code or a screenshot to see the final result for me as a quiet reader in this topic?

Stefan