144

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

My method:

\documentclass[UTF8]{ctexart}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{epstopdf}
\usepackage{inputenc}
\begin{equation}
\"{o}
\mathaccent{o} 
\end{equation}

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!!

7
  • 23
    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. Jan 8, 2014 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, 2014 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, 2014 at 3:27
  • 4
    $\hat{u}$....
    – user11232
    Jan 8, 2014 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, 2015 at 5:00

1 Answer 1

198

The sequence

\"{o}

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

\dot{o}
\ddot{o}

and so on, should do the trick.

Edit:

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

4
  • 1
    what package do you need in order to use \"? it does not seem to work by default.
    – elkshadow5
    Dec 12, 2021 at 0:03
  • It should work in the text mode without any additional packages. I checked with only \documentclass{article}\begin{document} Thr\"{o}ugh \end{document}
    – Cain
    Dec 13, 2021 at 11:37
  • How did you type \" ? When I try typing \", it does not work, but when I copy/paste your code, it does.
    – Allure
    Feb 28 at 9:00
  • 1
    It's simply a backslash and a double quotation mark.
    – Cain
    Mar 1 at 9:20

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