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I frequently use simple and larger parenthesis in math mode, like what is shown in the MWE below:

\documentclass[11pt,letterpaper,twoside]{book}
\usepackage{lmodern}
\usepackage{amsmath}
\usepackage{mathtools}

\newcommand*{\bigs}[1]{\vcenter{\hbox{\scalebox{1.25}{#1}}}}

\begin{document}

Blabla bla bla blabla :
    \begin{equation}
        \Big( c \, \bigs( \big( (1 + (x - y^2)(a + b) \big) \bigs) \Big) = \tfrac{3}{4}.
    \end{equation}

\end{document}

I usually don't use the \left \right variants, since I find them too big, and also for other reasons that aren't relevant here.

The \big( \big) commands give a nice output when the document is written in 12pt size. The difference with simple () is clear. But then, If I reduce the font to 11pt, the difference becomes very small, almost negligible. Why is that?

To solve this, I defined a small macro to give something between the simple parenthesis and the \Big version. But I'm now wondering why I have to do this and if this a proper way of doing things in LaTeX.

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Cham
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  • unrelated to the size question but you should not use \big or \Big etc in a document they are just the internal implementation of code shared between \big; and \bigr, it should be \Bigl(....\Bigr) – David Carlisle Dec 09 '19 at 00:30
  • I don't see any differences using \bigl and \bigr, and they make typing a bit longer. – Cham Dec 09 '19 at 00:32
  • The horizontal spacing is incorrect. \Big( is a mathord, \Bigl( is a mathopen. – David Carlisle Dec 09 '19 at 00:33
  • I don't see any horizontal difference (from the MWE above). Maybe that example isn't complicated enough? And what is a mathord? – Cham Dec 09 '19 at 00:35
  • \documentclass{article}

    \begin{document}

    $\sin{(}x{)} \rightarrow \sin(x)$

    $\sin\big(x\big) \rightarrow \sin\bigl(x\bigr)$

    \end{document}

     – David Carlisle Dec 09 '19 at 00:40
  • That's in text mode (I mean inside a text line). – Cham Dec 09 '19 at 00:45
  • I see the difference. But then, If I use {} for the trig functions, the spacing troubles is back. For example: \sin{\bigl( x \bigr)}. I usually put the trig argument inside {}. – Cham Dec 09 '19 at 00:49
  • I don't know what you mean by the last comment, but \big is simply wrong always, it may accidentally give the same spacing because a mathord and mathopen get the same space in some contexts but it is not supported document markup. – David Carlisle Dec 09 '19 at 00:49
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    putting the argument in {} destroys the spacing, why are you using braces? – David Carlisle Dec 09 '19 at 00:50
  • Because trig functions have an argument. – Cham Dec 09 '19 at 00:51
  • that isn't a reason for forcing tex to lose its classification of math constructs and so badly space the expression. The mathematical function has an argument but the tex command \sin does not so the braces are not absorbed by \sin as an argument, they instead coerce the (...) to start with a mathord not a mathopen, – David Carlisle Dec 09 '19 at 00:53
  • Hmm, then I'll have a nightmare in fixing my book. There are thousands of trig functions in there, using {} ! – Cham Dec 09 '19 at 00:54
  • But then this isn't solving the size issue with \bigl( \bigr), compared to () and \Bigl( \Bigr). – Cham Dec 09 '19 at 01:03
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    Q: "Why are you using braces?" A: "Because trig functions have an argument." Not in TeX and LaTeX! The correct syntax is $\sin(\theta_1+\theta_2)$. Note that $\sin{(\theta_1)}$ inserts too much whitespace between "sin" and "(" -- and is thus wrong from a typographic perspective. – Mico Dec 09 '19 at 05:18
  • Issues about spacing aside (just to be clear: I agree with David and Mico) your issue is due to an unfortunate setting of the lmodern fonts. If you comment out lmodern you'll see that the \big parentheses are in fact larger. See https://tex.stackexchange.com/a/137143/82917 (slightly different question but same reason) – campa Dec 09 '19 at 08:30
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    @Cham The problem is indeed the same as in https://tex.stackexchange.com/q/137141/4427 I'd close this one as duplicate, what do you think? – egreg Dec 09 '19 at 09:07
  • @campa, wow, now it's the font! Thanks a lot. Yep, you may mark my question as a duplicate. – Cham Dec 09 '19 at 10:05
  • According to https://tex.stackexchange.com/questions/175605/documentation-of-lmodern-package, a solution is to add an option to the lmodern package: \usepackage[nomath]{lmodern}. – Cham Dec 09 '19 at 10:44

1 Answers1

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The source of the problem is the lmodern font used. A solution is to add an option to that font by loading it with a nomath option (see the answer to this question: Documentation of lmodern package?):

\usepackage[nomath]{lmodern}

However, I'm now wondering about the values of the lmodern font. Why use it? What are its differences with the default computer modern? I don't see much differences, except for the integral signs (size again). About these fonts:

Is it still useful to load the lmodern package?

Cham
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