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I have a nested fraction on the right-hand side of an equation. I use the LaTeX code as follows to produce the equation:

\begin{equation}
\frac{1}{T_{ex}} = \frac{\frac{1}{T_{kin}}+\left(\frac{A_{ul}}{C_{ul}}        
\frac{T_{cmb}}{T_*}\right)\frac{1}{T_{cmb}}}{1+\frac{A_{ul}}{C_{ul}}    
\frac{T_{cmb}}{T_*}}.
\end{equation}

However, the fractions in the denominator and numerator of the main fraction appear too small on a regular A4 page. How can I make them larger while preserving the size of text on the left-hand side.

stars83clouds
  • 728

1 Answers1

26

(I swear this must be a duplicate question, but I can't find one.)

Read the comments below for why you might want to use a single \displaystyle instead of my answer below.

Use \cfrac: (Also, use \text{…} for math elements that are interpreted as text, such as \lim_{t\to\infty}C_{\text{Gasoline}=\infty})

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\cfrac{1}{T_{\text{ex}}} = \cfrac{\cfrac{1}{T_{\text{kin}}}+\left(\cfrac{A_{\text{ul}}}{C_{\text{ul}}}
\cfrac{T_{\text{cmb}}}{T_*}\right)\cfrac{1}{T_{\text{cmb}}}}{1+\cfrac{A_{\text{ul}}}{C_{\text{ul}}}
\cfrac{T_{\text{cmb}}}{T_*}}.
\end{equation}
\end{document}

enter image description here

Sean Allred
  • 27,421
  • I found an earlier, related posting... – Mico Oct 22 '14 at 05:18
  • @Mico can you link it here ? The question may still be duped. – Sean Allred Oct 22 '14 at 12:27
  • 1
    The earlier posting's title is Fractions with large elements. Personally, I think it's better to provide a \displaystyle declaration at the start of the numerator and denominator material than to employ a multitude of \cfrac directives. – Mico Oct 22 '14 at 13:33
  • @Mico Why would you say? I would use \cfrac, not only because it is less typing, but because (to me) it seems much more descriptive of the actual mathematics. Is there a disadvantage to using \cfrac that I'm as-of-yet ignorant of? – Sean Allred Oct 22 '14 at 13:43
  • @Mico Also, I didn't realize the question had already been duped -- you sacrifice a bit when you use the mobile app :) Reading the duped-answer makes a lot of sense now. – Sean Allred Oct 22 '14 at 13:44
  • Try typesetting \cfrac{\cfrac{u+v}{x+z}}{\cfrac{\alpha+\iota}{\nu+\epsilon}} and \ddfrac{\frac{u+v}{x+z}}{\frac{\alpha+\iota}{\nu+\epsilon}}, and you'll see that \cfrac adds a whole lot more whitespace than \displaystyle does. This is because \cfrac also inserts strut, which is taller and deeper than \mathstrut. – Mico Oct 22 '14 at 14:35