LaTeX provides a variety of commands for producing accented letters in math. These are different from accents in normal text (see Accents).
\acute Math acute accent
\bar Math bar-over accent
\breve Math breve accent
\check Math háček (check) accent
\ddot Math dieresis accent
\dot Math dot accent
\grave Math grave accent
\hat Math hat (circumflex) accent
\mathring Math ring accent
\tilde Math tilde accent
\vec Math vector symbol
\widehat Math wide hat accent
\widetilde Math wide tilde accent
When you are putting an accent on an i or a j, the tradition is to use one without a dot, \imath or jmath (see Math symbols).
© 2007–2018 Karl Berry
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http://latexref.xyz/Math-accents.html