7.78.1 Top new questions this week

7.78.1.1 Use recursion in LaTeX3

https://tex.stackexchange.com/landing/r/digest?cta=question&id=625320

I want to use recursion to calculate n! in LaTeX3, but found that the result is not correct, mwe is as follows 
\documentclass{article} 
\ExplSyntaxOn 
\cs_set:Nn \froac:n { 
\... 
[expl3]
 

asked by ljguo https://tex.stackexchange.com/landing/r/digest?cta=user&id=256849 15 votes

answered by Marcel KrA~\274ger https://tex.stackexchange.com/landing/r/digest?cta=user&id=80496 21 votes

7.78.1.2 Where does the extra space come from after a capital P in math mode?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=625795

Ia^\200\231ve noticed that when a capital P appears in juxtaposition with another variable in math mode, an extra space is automatically inserted. This appears to happens in both plain TeX and in LaTeX. Herea^\200\231s ... 
[math-mode] [tex-core]
 

asked by Alexis King https://tex.stackexchange.com/landing/r/digest?cta=user&id=72456 12 votes

answered by David Carlisle https://tex.stackexchange.com/landing/r/digest?cta=user&id=1090 11 votes

7.78.1.3 Off Diagonal matrix

https://tex.stackexchange.com/landing/r/digest?cta=question&id=625331

How to write off diagonal matrix in latex? 
I tried this 
\begin{align*} 
\left[ 
\begin{array}{ccccc} 
&  &  &  & 1 \\ 
&  &  & \ldots  \\ 
1 &... 
[math-mode] [formatting] [matrices]
 

asked by aamir farooq https://tex.stackexchange.com/landing/r/digest?cta=user&id=258239 8 votes

answered by Vincent https://tex.stackexchange.com/landing/r/digest?cta=user&id=201628 10 votes

7.78.1.4 replace capital a^\200\272a'\272\236a^\200\271 with a^\200\272ssa^\200\271 when using small caps

https://tex.stackexchange.com/landing/r/digest?cta=question&id=625781

I like small caps for author surnames. 
Until quite recently, capitalized a^\200\272A~\237a^\200\271 a^\200\223 a special character that is regularly used in the German alphabet a^\200\223 was replaced by a^\200\272SSa^\200\271 (in headings, small caps in ... 
[small-caps] [capitalization] [libertine] [german]
 

asked by Kubo https://tex.stackexchange.com/landing/r/digest?cta=user&id=134455 7 votes

answered by egreg https://tex.stackexchange.com/landing/r/digest?cta=user&id=4427 5 votes

7.78.1.5 \widering over \bar not working

https://tex.stackexchange.com/landing/r/digest?cta=question&id=626020

I need to write a topology expression involving the interior of the closure of a set. For the interior of a (not simple) set I'm using the macro \widering from yhmath package and it works fine if I ... 
[accents] [yhmath]
 

asked by Juan CastaA~+-o https://tex.stackexchange.com/landing/r/digest?cta=user&id=231368 5 votes

answered by egreg https://tex.stackexchange.com/landing/r/digest?cta=user&id=4427 1 vote

7.78.1.6 Tikz: Extract polar coordinate

https://tex.stackexchange.com/landing/r/digest?cta=question&id=625596

Is there a (simple) way to extract polar coordinates in Tikz? 
Motivation: I define two points (a) and (b) as intersection of a line and a circle (center at the origin) and then I want to an arc ... 
[tikz-pgf] [coordinates]
 

asked by Gilles Bonnet https://tex.stackexchange.com/landing/r/digest?cta=user&id=22655 5 votes

answered by Jasper Habicht https://tex.stackexchange.com/landing/r/digest?cta=user&id=47927 8 votes

7.78.1.7 Add label in Tikz

https://tex.stackexchange.com/landing/r/digest?cta=question&id=625935

the figure I try to create is below: (I try to make the same with the upper figure, the lower is mine but it seem to be not the same) 
My code: 
\begin{center} 
\begin{tikzpicture} [scale=0.5] 
\draw [... 
[tikz-pgf]
 

asked by user https://tex.stackexchange.com/landing/r/digest?cta=user&id=236730 5 votes

answered by Jasper Habicht https://tex.stackexchange.com/landing/r/digest?cta=user&id=47927 6 votes