# Break equation in parts

I want to break this equation in multi-line but unable to get it!

\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator{\E}{E}
\begin{document}
\begin{multline*}
\P_t=
\frac{1}{2}\Bigl(m_t+v_t-u_t
+(\frac{1-\zeta }{2})(\frac{E_{t-1}m_t+\frac{1-\zeta }{2\zeta }E_{t-
2}m_t+\frac{\zeta (1-\zeta )}{2(1+\zeta )}E_{t-2}P_{t-1}+\frac{\zeta }
{2}P_{t-1}+\frac{\zeta }{1+\zeta }P_{t-2}}{(1+\zeta )}))\bigr\\
+\frac{(1-\zeta )}{4}\Bigl(\frac{E_{t-2}m_t+(\frac{\zeta }{2})(E_{t-2}P_{t-
1}+P_{t-2})}{(1+\zeta )})\Bigr) \\
+\frac{\zeta }{4}(\Bigl((P_{t-1}+P_{t-2})\Bigr)
\end{multline*}
\end{document}

It's getting out of the mage, so I tired to break it but still it's not showing the correct showing. Can anyone help to identify the problem in coding? How to use breqn?

• )\bigr\\ is applying bigr to \\ presumably you intended \bigr)\\ May 27 '19 at 7:34
• I suggest you use the chktex program, which should be included in your distribution, to find unbalanced pairs of parentheses. May 27 '19 at 8:18

You overuse parentheses. If I've well understood your formula, here is a layout which fits on two lines, with the geometry package, to have more decent margins. Also, I prefer to use the medium-size fractions from nccmath for fractionary coefficients:

\documentclass{article}
\usepackage[showframe]{geometry}
\usepackage{amsmath, nccmath}
\DeclareMathOperator{\E}{E}

\begin{document}
\vspace*{2ex}
\begin{multline*}
\P_t=
\mfrac{1}{2}\biggl(m_t+v_t-u_t
+\frac{1-\zeta }{2}\,\frac{E_{t-1}m_t+\frac{1-\zeta }{2\zeta }E_{t-2}m_t+\frac{\zeta (1-\zeta )}{2(1+\zeta )}E_{t-2}P_{t-1}+\frac{\zeta }{2}P_{t-1} +\frac{\zeta }{1+\zeta }P_{t-2}}{1+\zeta}\biggr) \\
+\frac{1-\zeta }{4}\,\frac{E_{t-2}m_t+\frac{\zeta }{2}(E_{t-2}P_{t-1}+P_{t-2})}{1+\zeta} +\frac{\zeta }{4}(P_{t-1}+P_{t-2})
\end{multline*}

\end{document}

• Thanks, I got my mistake. May 27 '19 at 9:48
• I think you should replace \P_t with P_t... And, since the preamble features the instruction \DeclareMathOperator{\E}{E}, you may also want to replace all intstances of E in the mathy material with \E.
– Mico
May 27 '19 at 10:57
• Before suggesting making "more decent margins", please consider the final destination of the document. If it's submitted for publication in a journal, and the page size of the journal is too narrow to accommodate the display, you run the risk of having changes made in the editorial process possibly leading to a change in meaning or actual errors. Such formatting adjustments are much better made by the author. May 27 '19 at 11:53
• @barbarabeeton: You're right, I should have added 'if wide margins are not required'. I'm not sure most people really need these very wide margins, unless they use marginal notes. May 27 '19 at 13:05

I would simplify the formula first and then typeset it across three rows using an align* environment.

\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator{\E}{E}  % expectations operator

\begin{document}
\begin{align*}
P_t
&=\frac{1}{2}(m_t+v_t-u_t)
+\frac{1}{4}\frac{1-\zeta}{1+\zeta}
\biggl[\E_{t-1}m_t +\frac{1-\zeta}{2\zeta }\E_{t-2}m_t\\
+\frac{\zeta}{2}P_{t-1}+\frac{\zeta}{1+\zeta }P_{t-2}
+\E_{t-2}m_t\\
+\frac{1}{4}\zeta (P_{t-1}+P_{t-2})
\end{align*}
\end{document}
• That's a really cool way to represent it. Didn't think of it, thanks a lot! May 27 '19 at 11:25

After removing all unnecessary brackets, correcting size of used ones, with use nccmath for medium size fractions and changed lines of equation:

\documentclass{article}
\usepackage{nccmath}
%---------------- show page layout. don't use in a real document!
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}

\begin{document}
\begin{multline*}
P_t=
\frac{1}{2}\Biggl(m_t+v_t-u_t           \\
+ \frac{1-\zeta }{2}\frac{E_{t-1}m_t
+ \mfrac{1-\zeta}{2\zeta}E_{t-2}m_t
+ \mfrac{\zeta(1-\zeta)}{2(1+\zeta)}E_{t-2}P_{t-1}
+ \mfrac{\zeta}{2}P_{t-1}
+ \mfrac{\zeta}{1+\zeta}P_{t-2}}
{1+\zeta}\Biggr)                \\
+ \frac{1-\zeta}{4}
\frac{E_{t-2}m_t + \frac{\zeta}{2}(E_{t-2}P_{t-1}
+ P_{t-2})}{1+\zeta}
+ \frac{\zeta }{4}\Bigl(P_{t-1}+P_{t-2}\Bigr)
\end{multline*}
\end{document}

(red lines indicate text borders)

• Thanks a lot, it clearly answers my question. May 27 '19 at 9:47
• I would replace \Pi_t with P_t...
– Mico
May 27 '19 at 11:19
• @Mico, done! Thank you very much! May 27 '19 at 11:33