the two dots above a letter represents two derivative of varible t.

My method:


However,the latex says in the math environment ,I must use the \mathaccent. So I replace \" by \mathaccent, but it shows the warning information: Missing number, treated as zero

I am a starter, I want to know how to revise it? Can someone help me? Thanks sincerely!!

  • 18
    Welcome to TeX.SE. Use $\dot x$ for the first derivative, \ddot x for the second, \dddot x for the third, \ddddot x for the fourth. – Peter Grill Jan 8 '14 at 3:03
  • @Peter Grill,Thaks for your warm welcome and solution.I am a college student.I like Latex very much. – mma Jan 8 '14 at 3:08
  • @ Peter Grill,Dear Peter Grill,BTW,how to write the "^" above a letter.\^{u} cannot achieve that effect in the math enviroment. – mma Jan 8 '14 at 3:27
  • 4
    $\hat{u}$.... – user11232 Jan 8 '14 at 3:45
  • I would like to extend this question and ask how one would do the same thing only under the letter or a word – tmwitten Jul 27 '15 at 5:00

The sequence


will be used when you want to write 'ö' in text, such as 'Schrödinger'. While in the math mode, as Peter Grill mentioned


and so on, should do the trick.


For more than two dots, e.g. \dddot{o}, you need the package amsmath, which allows you a maximum of 4 dots \ddddot{o} (not strikingly beautiful fourth time derivative)

For higher dot derivatives take a look at this post


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