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}}}.
    – egreg
    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)?
    – user32680
    Jun 27, 2013 at 15:58
  • 4
    @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.
    – Christian
    Jun 27, 2013 at 16:38

1 Answer 1


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:



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


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


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


enter image description here


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