# Split of equation isn't arrange properly

Question: Is it possible to achieve the image shown below using my codes?

MWE:

\documentclass[12pt,a4paper]{article}
\usepackage[width=1.00in, height=1.00in, left=1.00in, right=1.00in, top=1.00in, bottom=1.00in]{geometry}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{hyperref}
\usepackage{mathtools}
\usepackage{amsthm}
\begin{document}
\begin{flalign}
&\begin{multlined}
\dfrac{\partial T}{\partial t}+u\;\dfrac{\partial T}{\partial x} + v\;\dfrac{\partial T}{\partial y}
=\left(\dfrac{k_{2}}{\rho\,c_{p}}\right)\,\dfrac{\partial^2 T}{\partial y^2}+\dfrac{Q_{0}}{\rho\,c_{p}}\left(T-T_{\infty}\right)+\dfrac{1}{\rho\,c_{p}}\;\dfrac{16\sigma^{*}}{3 k^{*}}\,\left[3T^{2}\,\dfrac{\partial T}{\partial y}+T^{3}\,\dfrac{\partial^2 T}{\partial y^2}\right]\\[2ex]
+\dfrac{DK_{T}}{c_{s}\,c_{p}}\,\dfrac{\partial^2 C}{\partial\,y^2}
\end{multlined}
\end{flalign}
\end{document}

• Why do you think that line 2 should be centered if you use multlined? To me it does exactly what it is suppose to. It centers left aligns the first row, right aligned the last row and centered the others (at least that is what the full multline does). You only have two lines. Commented Jul 25 at 9:08
• I would not use multlined at all. Manually specify where you want the alignment. Commented Jul 25 at 9:09
• I just wanted to shift the equation number to the center of those two lines. Commented Jul 25 at 9:10
• also don't use flalign here either don't use alignments for single row equations Commented Jul 25 at 9:10
• Then use equation plus aligned Commented Jul 25 at 9:23

Even moving the last piece to the left won't be enough to have a centred equation number: the line is just too long. Break it elsewhere:

\documentclass[12pt,a4paper]{article}
\usepackage[margin=1in]{geometry}% simpler than specifying each margin
\usepackage{amssymb}
\usepackage{mathtools}
\usepackage{amsthm}
\usepackage{hyperref}% should be last (with very few exceptions)

\begin{document}
\begin{aligned} \dfrac{\partial T}{\partial t}+u\;\dfrac{\partial T}{\partial x} + v\;\dfrac{\partial T}{\partial y} ={}&\left(\dfrac{k_{2}}{\rho\,c_{p}}\right)\,\dfrac{\partial^2 T}{\partial y^2}+\dfrac{Q_{0}}{\rho\,c_{p}}\left(T-T_{\infty}\right) \\ &+\dfrac{1}{\rho\,c_{p}}\;\dfrac{16\sigma^{*}}{3 k^{*}}\,\left[3T^{2}\,\dfrac{\partial T}{\partial y}+T^{3}\,\dfrac{\partial^2 T}{\partial y^2}\right] +\dfrac{DK_{T}}{c_{s}\,c_{p}}\,\dfrac{\partial^2 C}{\partial\,y^2} \end{aligned}
\end{document}


I can't say that I like all manual spacings you introduce, or the pointless use of \dfrac here, or the use of \left/\right but that's personal taste.

• nice answer, however, you should mentioned that hyperref should be loaded last. Commented Jul 25 at 9:19
• It's easy. Thank you. any other better option than \dfrac Commented Jul 25 at 9:21
• @SandyM dfrac does nothing here that normal frac doesn't already do. You are already in display math Commented Jul 25 at 9:24
• @Zarko Ups, of course you're right, hadn't noticed that. Commented Jul 25 at 10:24

I see no reason for flalign (and you should use it sparingly, if at all).

A split is what you want.

I changed \; to \, and removed almost all \,. Between a symbol and a fraction or two fractions a thin space might be a good choice (be consistent), but definitely no thin space should go between \rho and c_p. Also remember that \left and \right already make thin spaces around the fenced subformula, so there's no need to add space again.

I'd prefer the second way.

\documentclass[12pt,a4paper]{article}
\usepackage[
%width=1.00in,  % <--- wrong
%height=1.00in, % <--- wrong
left=1.00in,
right=1.00in,
top=1.00in,
bottom=1.00in
]{geometry}
%\usepackage{amsmath}
\usepackage{mathtools}
\usepackage{amssymb}
\usepackage{amsthm}% <--- should go before hyperref
\usepackage{hyperref}

\begin{document}

$$\begin{split} \frac{\partial T}{\partial t} + u\,\frac{\partial T}{\partial x} + v\,\frac{\partial T}{\partial y} ={}& \left(\frac{k_{2}}{\rho c_{p}}\right)\frac{\partial^2 T}{\partial y^2} + \frac{Q_{0}}{\rho c_{p}}(T-T_{\infty}) + \frac{1}{\rho c_{p}}\,\frac{16\sigma^{*}}{3 k^{*}} \left[3T^{2}\,\frac{\partial T}{\partial y}+T^{3}\,\frac{\partial^2 T}{\partial y^2}\right] \\ &+\frac{DK_{T}}{c_{s}c_{p}}\,\frac{\partial^2 C}{\partial y^2} \end{split}$$

$$\begin{split} \frac{\partial T}{\partial t} + u\,\frac{\partial T}{\partial x} + v\,\frac{\partial T}{\partial y} ={}& \left(\frac{k_{2}}{\rho c_{p}}\right)\frac{\partial^2 T}{\partial y^2} + \frac{Q_{0}}{\rho c_{p}}(T-T_{\infty}) \\ &+ \frac{1}{\rho c_{p}}\,\frac{16\sigma^{*}}{3 k^{*}} \left[3T^{2}\,\frac{\partial T}{\partial y}+T^{3}\,\frac{\partial^2 T}{\partial y^2}\right] +\frac{DK_{T}}{c_{s}c_{p}}\,\frac{\partial^2 C}{\partial y^2} \end{split}$$

\end{document}