The simplest workaround is omitting the big parentheses: \log x
has been considered the same as \log(x)
for a few centuries and it continues to be. If the argument to the logarithm is a fraction, there's no doubt whatsoever what the logarithm applies to.
Thus type
\ln\frac{\dfrac{( x \times y)^{z}}{( (R)^{z} \times A )}}{B}
with no \left
and \right
, which serve no purpose here. Also the \displaystyle
declarations are useless (and also a bit wrong).
Lowering the big fraction to get smaller parentheses is wrong: it will make very unclear what the main fraction line is. Beware that A/(B/C)
is AC/B
, whereas (A/B)/C
is A/(BC)
, quite different things. Having \ln
aligned with the middle row in the three story fraction will generate doubts in your readers. The fact one line is slightly longer than the other will not help at all: have mercy of your readers with weak sight. Multiple story fractions are never interpreted “top to bottom”:
A
–
B
x = –
C
–
D
is interpreted as AD/BC
and not as ((A/B)/C)/D
which is A/(BCD)
. The position of the main fraction line on the formula axis makes the meaning clear.
This said, choose between the three following proposal: as usual in the order good, bad and ugly from top to bottom.
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
\ln\left(\frac{1}{B}\frac{( x \times y)^{z}}{R^{z} \times A}\right)
\]
\[
\ln\frac{\dfrac{( x \times y)^{z}}{R^{z} \times A}}{B}
\]
\[
\ln\left(
\begin{gathered}
\frac{\;\dfrac{( x \times y)^{z}}{R^{z} \times A}\;}{B}
\end{gathered}
\right)
\]
\end{document}
\displaystyle
? it should almost never be used.\[ T = \ln\left(\frac{(x \times y)^z}{B(R^z \times A)}\right) \]
?