arc notation for geometry

[CC]

I am trying to create notations for arcs of circles (with a curve over two to three capital letters) and I am unable to find that symbol in any of the notations.

Thanks for your time.

[firemath]

Within Firemath there is an 'OverParenthesis' button in the tabs panel at 'miscellaneous operators'. Enclose your capital letters by an <mrow> and add <munderover>-elements to that <mrow>. Place the OverParenthesis as the <mover>-element. Set the stretchy-attribute of the OverParenthesis to true.

Unfortunately, Firefox seems to have some bugs with respect to stretchy operators. See
https://bugzilla.mozilla.org/show_bug.cgi?id=416065
https://bugzilla.mozilla.org/show_bug.cgi?id=416140

If I misunderstood your question, it might help if you publish a LaTeX-expression here demonstrating what you intend to do.