# Delimiting equations in math mode

I'm trying to delimit an equation with parentheses and it has fractions inside it, so I can't just increase the parentheses' size, because they wouldn't be correctly alligned. What I'm trying to do is the following:

MDC(m,n)=mindiv(m,n)$\times$ MDC $\left($ $\dfrac{m}{mindiv(m,n)}$,$\dfrac{n}{mindiv(m,n)}$ $\right)$


It compiles correctly until I attempt to add the parentheses like that. I've tried all possible ways to add the math mode delimiters, but all it does is give me a series of errors. How do I delimit bigger equations like this in math mode? I found out that the following works:

$\left( \right)$


However, if I attempt to wrap the equation like that (with the delimiters at the beginning and at the end only), I still get a series of errors.

• ...then you haven't "tried all possible ways"... – Werner Apr 8 '15 at 21:20
• Yeah, indeed I hadn't. I have just had an insight which actually worked. – Vinicius Sesti Apr 8 '15 at 21:21
• Welcome to TeX.SX! Why are you jumping out of mathmode continously? – user31729 Apr 8 '15 at 21:21
• Thank you! I had initially thought I needed to delimit math mode whenever I wanted to add a math symbol, only now I found out I would jump in and out of math mode doing that. A single pair of delimiters wrapping the entire piece of code is enough, apparently. – Vinicius Sesti Apr 8 '15 at 21:24

You're doing it wrong...

You should switch to math-mode and stay there in order to set math content:

\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator{\mindiv}{mindiv}
\DeclareMathOperator{\MDC}{MDC}
\begin{document}
$\MDC(m,n) = \mindiv(m,n) \times \MDC \biggl( \dfrac{m}{\mindiv(m,n)}, \dfrac{n}{\mindiv(m,n)} \biggr)$
\end{document}


I've declared some operators since it seemed to suit your needs. Also, you can use \left(...\right), but I've decided (for spacing consistency) to use \big-like delimiters.

Jumping out of mathmode using $...$ is not a pretty good way. Use a common $...$ pair or $...$ or a math environment as equation or align.

The function names should be wrapped into a \DeclareMathOperator statement to provide upright typesetting and better spacing, however, admitted, I had done this only for \mindiv so far. I leave it to the OP as an exercise for the \MDC operator ;-)

\documentclass{article}

\usepackage{mathtools}

\DeclareMathOperator{\mindiv}{mindiv}

\begin{document}

$MDC(m,n)=\mindiv(m,n) \times MDC \left(\dfrac{m}{\mindiv(m,n)},\dfrac{n}{\mindiv(m,n)}\right)$

\begin{align}
MDC(m,n) &=\mindiv(m,n) \times MDC \left(\dfrac{m}{\mindiv(m,n)},\dfrac{n}{\mindiv(m,n)}\right)
\end{align}

\end{document}


• MDC is wrong: if you want italics it should be \mathit{MDC}. – egreg Apr 8 '15 at 21:29
• @egreg: See the 'explanation' in the post ;-) – user31729 Apr 8 '15 at 21:29