# Re: problem displaying angstrom symbol

On 2014-05-06, Jens Nöckel wrote:

> On May 6, 2014, at 8:45 AM, Ider Ronneberger wrote:

>> Hi,

>> I have a problem in lyx displaying the angstom symbol using \AA within
>> the math mode, i.e. if I want to view the document as pdf the angstrom
>> sign is not there. However it works if I write \AA in Tex mode or
>> insert it from Insert>Special Charecters> Symbols...

>> On the bottom pane of the lyx display, there is a short info message.
>> In one case it says "Type: simple Macro:AA" and in the other case (
>> which works) it just says "Type: simple". What is the difference? How
>> can resolve this issue?

> The problem is that \AA is a text mode command, not meant for equation
> environments. In LyX, I get the correct output if I enter the Å symbol
> from the keyboard (shift-option-A on the Mac). In an equation, LyX then
> replaces that symbol by \mathring{A}, which displays properly in the
> PDF output. So you could alternatively also enter \mathring{A} in the
> LyX math editor.

Depending on what it should stand for, the correct approach is to nest it in
a text box or use \mathring{A} instead of \AA:

\mathring{A} is usually printed in italics, it stands for a variable
(just like x and y).

\mathrm{\AA} or \text{AA} are usually printed upright (roman) and stand
for a constant or the length unit Ångström (10 nm).

All SI units (and also most non-SI units) should be written upright.
This is also often done wrong for the micro prefix µ.

Günter