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I am writing some complicated formulas that involve several layers of fractions.

Example:

\begin{displaymath}
\scalebox{2.5}[3]%
{$
1+\frac{1^2}{2+\frac{3^2}{2+\frac{5^2}{2+\frac{7^2}{2+\frac{9^2}{2+\cdots}}}}}
$}
\end{displaymath}

but the visual result, although readable, could be improved with some white space over all the squared odd terms. How would I achieve that? The vertical scaling of \scalebox does not help since I guess that the spacing between the fraction line and the exponent under it is too close to zero.

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3 Answers 3

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Warning: Mico's solution is better (see below). With mine, the edges of the fractional expressions are not perfectly aligned on the right.

You could use \dfrac and \mathstrut:

\documentclass{article}
\usepackage{amsmath}

\begin{document}
    \begin{displaymath}
        1+\dfrac{1^2}{2+\dfrac{3^{\mathstrut 2}}{2+\dfrac{5^{\mathstrut 2}}{2+\dfrac{7^{\mathstrut 2}}{2+\dfrac{9^{\mathstrut 2}}{2+\cdots}}}}}
    \end{displaymath}
\end{document}

enter image description here

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  • Great! I did not know about \mathstrut
    – marco trevi
    Dec 2, 2017 at 9:17
  • @marcotrevi Look at this: tex.stackexchange.com/questions/41185/…
    – CarLaTeX
    Dec 2, 2017 at 9:20
  • 2
    @marcotrevi Thank you for accepting my answer but Mico's one is better, see the end of the fraction lines, they are not perfectly aligned.
    – CarLaTeX
    Dec 2, 2017 at 9:25
10

Load the amsmath package and use its \cfrac ("continued fraction") macro:

enter image description here

\documentclass{article}
\usepackage{amsmath} % for \cfrac macro
\begin{document}
\begin{displaymath}
1+\cfrac{1^2}{2+\cfrac{3^2}{2+\cfrac{5^2}{2+\cfrac{7^2}{2+\cfrac{9^2}{2+\cdots}}}}}
\end{displaymath}
\end{document}

The main difference to a \dfrac-based solution is that, with \cfrac, the right-hand edge of the fractional expressions is nice and vertical, which is not the case if \dfrac is used repeatedly.

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    @CarLaTeX And you might enjoy a simplified syntax for continued fractions: tex.stackexchange.com/a/43412/4427
    – egreg
    Dec 2, 2017 at 9:14
  • Great! It's not super neat with other formulas though
    – marco trevi
    Dec 2, 2017 at 9:15
  • @marcotrevi - Please give an example or two of "other formulas" which don't look "super neat" when using \cfrac. (It's not easy to respond to a generic, non-specific comment...)
    – Mico
    Dec 2, 2017 at 9:18
  • @egreg Of course, a LaTeX3 solution must make an appearance!
    – CarLaTeX
    Dec 2, 2017 at 9:30
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    @CarLaTeX - Thanks, but don't fret or worry about it. These things do tend to even out in the medium to long term. In the past, I'm sure that some of my answers received ticks when others were at least as deserving. :-)
    – Mico
    Dec 2, 2017 at 13:20
2

If you are printing more continued fractions in your document then you can define the macro \cfraction which gives you more compendious source:

\def\cfraction{\def\cfracE{}\cfracA}
\def\cfracA#1+#2{#1\ifx#2\relax +\cdots\cfracE \else 
   + \bgroup \xdef\cfracE{\cfracE\egroup} \strut #2\expandafter\cfracB \fi}
\def\cfracB#1\over{#1\over \displaystyle\cfracA}


$$
\cfraction 
1 + 1^2 \over 2 + 3^2 \over 2 + 5^2 \over 2 + 7^2 \over 2 + 9^2 \over 2 + \relax
$$

\bye
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  • 1
    There's no drifting of the fraction lines if you add \kern-\nulldelimiterspace after \egroup
    – egreg
    Dec 2, 2017 at 11:01
  • OK, but the "drifting of fraction lines" is more aesthetic from my point of view.
    – wipet
    Dec 2, 2017 at 11:31

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