LaTeX How to Represent Complex Fractions in LaTeX?

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Two methods for representing complex fractions in LaTeX are discussed: using nested \dfrac commands and a format with superscripts and subscripts. To create a longer middle division line, LaTeX spaces can be added to the numerator or denominator. Regular spaces act as separators and may not render as expected, while specific LaTeX spaces like "~" and "\," are recommended for creating visible gaps. The use of the physics package is suggested for better spacing in integrals, which can also help with upright notation for differentials. Proper spacing in LaTeX is essential for clarity in mathematical expressions.
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TL;DR Summary
Exploring different ways to represent a complex fraction using LaTeX
I know of two reasonable ways to represent a complex fraction:
\dfrac{ \left ( \dfrac{a}{b} \right ) }{ \left ( \dfrac{c}{d} \right ) }
##\dfrac{ \left ( \dfrac{a}{b} \right ) }{ \left ( \dfrac{c}{d} \right ) }##

and
\dfrac{ ^a / _b }{ ^c / _d }
##\dfrac{ ^a / _b }{ ^c / _d }##

What I am wondering is if there is a way to write
##\dfrac{ \dfrac{a}{b} }{ \dfrac{c}{d} }##
by making a longer middle division line?

Thanks!

-Dan
 
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Hey Dan,

One way to make the middle line longer, is to add latex spaces to numerator or denominator.
For instance:
\dfrac{\;\dfrac ab\;}{\dfrac cd}
##\dfrac{\;\dfrac ab\;}{\dfrac cd}##
 
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I like Serena said:
add latex spaces to numerator or denominator
Sometimes I have to add explicit "~" characters to force spaces in LaTeX, but other times just " " spaces seem to work. I haven't figured out why yet...
 
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berkeman said:
Sometimes I have to add explicit "~" characters to force spaces in LaTeX, but other times just " " spaces seem to work. I haven't figured out why yet...
Can you give some examples?
 
berkeman said:
Sometimes I have to add explicit "~" characters to force spaces in LaTeX, but other times just " " spaces seem to work. I haven't figured out why yet...
Regular spaces are generally used as separator. For instance in \dfrac ab the space is not an actual space, but instead it's a separator. That separator only "becomes" a space, if that is needed to separate both sides. In that case multiple spaces are collapsed to a single space.
If we actually "want" a space where that is not already natural, we have to use one of the latex spaces like:
\! \, \: \; \quad \qquad, which are increasingly wide spaces. The first one is a negative space. The "~" is special in that it creates a non-breaking space, so that it won't "wrap".
 
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Orodruin said:
Can you give some examples?
Just a quick example:
$$v(t) = L \frac{di(t)}{dt}$$
$$v(t) = L~\frac{di(t)}{dt}$$
from:
1662414182567.png
 
The classical example is an integral: $$\int f(x,y) dx dy$$
Often \, is inserted (despite already having spaces) before the infinitesimals to get a more natural formula:$$\int f(x,y)\,dx\,dy$$
A "~" also works of course.
 
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berkeman said:
Just a quick example:
$$v(t) = L \frac{di(t)}{dt}$$
$$v(t) = L~\frac{di(t)}{dt}$$
from:
View attachment 313827
I meant examples of where you would expect a space but there was none.

I like Serena said:
A "~" also works of course.
Compare the following:
$$
\int f(x,y)~dx~dy \qquad \int f(x,y)\,dx\,dy
$$
The non-breaking space ~ is a regular sized space (it is equivalent in size to the regular \ ) as compared to \, which is 3 mu. The latter is typically what you want. The non-breaking space ~ should be used when you have a space where you do not wish to create a (line or page) break. In an equation it is essentially equivalent to the regular space "\ " (which has its own uses in text as well, such as not creating a too large space after an abbreviation, i.e., LaTeX will interpret "cf. last chapter" as there being an end of sentence after cf. whereas "cf.\ last chapter" will not).
 
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Orodruin said:
I meant examples of where you would expect a space but there was none.
In the first LaTeX line, I put a " " space after the L, but it did not render. It took the explicit "~"space after the L to get it to render.
 
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berkeman said:
In the first LaTeX line, I put a " " space after the L, but it did not render. It took the explicit "~"space after the L to get it to render.
Of course it didn’t, spaces are mostly irrelevant to math mode (for good reason).
 
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For integrals, using the physics package might be helpful to some extent. One may use \dd{} from that package, which manages the spacing automatically, and also makes the d upright.
$$\require{physics}
\int f(x,y) \dd{x} \dd{y}$$
 
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