I need to use | with the mean of "such that". It's in an expression with fraction and so I need to have a big |. I've tried to use \displaystyle before | but it doesn't work. Putting \left before | work, but Texstudio give an error because there isn't any \right. What can I do?

  • 2
    you can always size it with an wxplicit size. \bigg might be appropriate. – barbara beeton Jun 20 '18 at 18:26
  • Please accept an answer if you have found a solution. By the way, I would recommend zyy's answer, as this will scale with the content! – nox Jun 20 '18 at 19:12

I find the ‘middle’ commands look better for this:



\left.\frac{\partial f(x, y)}{\partial x}\right| f(t) = t^2 + 1
 \frac{\partial f( x, y)}{\partial x}\biggm| f(t) = t^2 + 1


enter image description here


If you want only a left delimiter but not a right one, you can use \left| \right. (with a dot).


You could do the following

\left. \frac{\partial f \left( x , y \right)}{\partial x} \right|_{x = 0}

This will yield


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    What's the purpose of writing f \left( x , y \right) instead of, say, f(x,y)? Put differently, why make (La)TeX insert whitespace between f and (? – Mico Jun 20 '18 at 20:45
  • @Mico LaTeX just recognize \left( \right) as occupying more space, I kind of have the habit of using \left( \right) instead of ( ) for all situation so that my document is more consistent. – zyy Jun 20 '18 at 21:08
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    "...so that my document is more consistent." You know what Ralph Waldo Emerson had to say about consistency, right? If not, here goes: "A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines. With consistency a great soul has simply nothing to do. He may as well concern himself with his shadow on the wall." (excerpt from an essay, entitled "Self-Reliance") Ouch! :-) – Mico Jun 22 '18 at 8:14
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    In case you're still not convinced that using \left and \right for the sake of consistency is maybe not all that great an idea, do check out the posting Is it ever bad to use \left and \right? – Mico Jun 23 '18 at 17:33
  • 1
    @Mico Yeah, that makes sense. – zyy Jun 28 '18 at 14:47

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