# The size of roots

I can't get to the root of this problem: I need the second root to be the same height as the first one

$\sqrt{F} \: \sqrt{F_{x_x}}$


I know I can use \vphantom, but I don't know how.

• Just add \vphantom{F_{x_x}} to the first square root: \sqrt{F\vphantom{F_{x_x}}}. Jun 27, 2013 at 15:55
• Thanks for your reply. But what if I want to make the second root "smaller" (small as the first root)? Jun 27, 2013 at 15:58
• @user32680 With amsmath loaded you can do $\sqrt{F} \: \sqrt{\smash[b]{F_{x_x}}}$. Jun 27, 2013 at 16:03
• -1 for the abysmal pun. ... ok, just kidding. Jun 27, 2013 at 16:38

Aligning square roots in the same formula requires some work if the symbols under the square root are not uniform in height and depth.

You can either add a phantom to the first square root or smash the bottom of the second one:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

$\sqrt{F} + \sqrt{F_{x_x}}$  % original

\medskip

$\sqrt{F\vphantom{F_{x_x}}} + \sqrt{F_{x_x}}$ % phantom

\medskip

$\sqrt{F} + \sqrt{\smash[b]{F_{x_x}}}$ % smash

\end{document}