# Taller than normal parallel symbol ||

I'd love to achieve a nice format for the following snippet:

$$Z_{eq}(j\omega) = R_0 + \left(R_1 + \frac{1}{j\omega C_1}\right) || \left(R_2 + \frac{1}{j\omega C_2}\right)$$

If printed as such, the || bars aren't tall enough to get a nice result.

I've also tried this solution but it doesn't work either.

$$Z_{eq}(j\omega) = R_0 + \left(R_1 + \frac{1}{j\omega C_1}\right)\parallel \left(R_2 + \frac{1}{j\omega C_2}\right)$$

Thank you!

As @DavidCarlisle has already noted in a comment, you may want to replace \parallel with \Vert. Importantly, the symbol produced by \Vert can be enlarged vertically with the help of the \big, \Big, \bigg, and \Bigg prefixes: \big\Vert, \Big\Vert, \bigg\Vert, and \Bigg\Vert. Finally, in case you need a bit of extra spacing around the double vertical lines, you could use the additional prefix element m: \bigm\Vert, \Bigm\Vert, \biggm\Vert, and \Biggm\Vert.

\documentclass{article}
\usepackage{amsmath} % for 'split' environment
\begin{document}
$\begin{split} Z_{\mathrm{eq}}(j\omega) &= R_0 + \biggl(R_1 + \frac{1}{j\omega C_1}\biggr) \bigg\Vert \biggl(R_2 + \frac{1}{j\omega C_2}\biggr)\\[1ex] &= R_0 + \biggl(R_1 + \frac{1}{j\omega C_1}\biggr) \biggm\Vert \biggl(R_2 + \frac{1}{j\omega C_2}\biggr) \end{split}$
\end{document}

• I believe this is a case for equation and split rather than align. Feb 16, 2020 at 17:26
• @egreg - Good idea. Done.
– Mico
Feb 16, 2020 at 18:30

Here's a macro that seems to work well:

\newcommand{\scaleparallel}[2]{
\left. {#1} \middle| \kern-0.1em \middle| {#2} \right.
}


Example that also uses the \align and \frac macros from the amsmath package:

Let
\begin{align}
Z_1 &= \scaleparallel{\frac{1}{sC}}{R} \\
Z_2 &= \scaleparallel
{
\frac
{
\scaleparallel
{R_1 + \scaleparallel{R_2}{R_3}}
{\left( R_2 + R_3 \right)}
}
{2}
}
{R_4}
\end{align}


Here is an in-line example: $$\scaleparallel{\frac{1}{sC}}{\left( -\frac{-b\pm \sqrt{b^2-4ac}}{2a} \right)}$$