9.30.1 Top new questions this week

9.30.1.1 How do I write LaTeX code for matrices of this form?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684958

I want to write code for a matrix of the form given in the picture below. How can I do it? 
What I have tried is the following code: 
\begin{bmatrix} 
a &      r &      0 & \dots \\ 
... 
[math-mode] [matrices]
 

asked by Mr.Gandalf Sauron https://tex.stackexchange.com/landing/r/digest?cta=user&id=296477 Score of 10

answered by Mico https://tex.stackexchange.com/landing/r/digest?cta=user&id=5001 Score of 12

9.30.1.2 I use color with left color, right color and fill in tikz, but why are these two cases differenti"\274\237

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684932

\begin{tikzpicture} 
\draw[left color=BlueGreen,right color=BlueGreen] (0,0) rectangle (2,1); 
\end{tikzpicture} 
\begin{tikzpicture} 
\draw[fill=BlueGreen] (0,0) rectangle (2,1); 
\end{tikzpicture} 
The ... 
[tikz-pgf]
 

asked by robot https://tex.stackexchange.com/landing/r/digest?cta=user&id=296460 Score of 7

answered by Ulrike Fischer https://tex.stackexchange.com/landing/r/digest?cta=user&id=2388 Score of 8

9.30.1.3 How to correct spacing between `=` under the SUM sign when using breqn package?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684816

In this MWE 
\documentclass[12pt]{book} 
\usepackage{amsmath} 
\usepackage{breqn} 
\newcommand{\myEquation}{\sum_{n=0}^{\infty} x^{n +5} a_{n} = \sum_{n=5}^{\infty}a_{n -5} x^{n} } 
\begin{document} 
\... 
[spacing] [typography] [breqn]
 

asked by Nasser https://tex.stackexchange.com/landing/r/digest?cta=user&id=14594 Score of 7

answered by egreg https://tex.stackexchange.com/landing/r/digest?cta=user&id=4427 Score of 2

9.30.1.4 Text not respecting \text within NewDocumentCommand within align*

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684710

Within an align* environment I have lines of the form 
\Rightarrow &<\texttt{Program Code}, [a \mapsto 1, b \mapsto 2]> &\text{Rule Name}\\ 
\Rightarrow &<\texttt{Program Code 2}, [... 
[align] [xparse]
 

asked by Harith https://tex.stackexchange.com/landing/r/digest?cta=user&id=233118 Score of 7

answered by Clara https://tex.stackexchange.com/landing/r/digest?cta=user&id=238422 Score of 7

9.30.1.5 Creating various road symbols with TikZ

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684899

I am trying to create three road symbols with TikZ. These are 
US Interstate Shield 
US Highway Shield 
Generic State Highway "pill". This is basically a rectangle capped with two semi-... 
[tikz-pgf]
 

asked by Logan https://tex.stackexchange.com/landing/r/digest?cta=user&id=270870 Score of 6

answered by Juan CastaA~+-o https://tex.stackexchange.com/landing/r/digest?cta=user&id=231368 Score of 9

9.30.1.6 Delete string up to last slash

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684769

\documentclass{article} 
\usepackage{xstring} 
\begin{document} 
\StrBehind[2]{/foo/bar}{/} 
\StrCount{/foo/bar}{/} 
\StrBehind[\StrCount{/foo/bar}{/}]{/foo/bar}{/} 
\end{document} 
I'm trying to delete /... 
[xstring]
 

asked by Michel Charpentier https://tex.stackexchange.com/landing/r/digest?cta=user&id=171866 Score of 6

answered by wipet https://tex.stackexchange.com/landing/r/digest?cta=user&id=51799 Score of 11

9.30.1.7 Drawing recursive polygons in Tikz

https://tex.stackexchange.com/landing/r/digest?cta=question&id=685076

To draw different kinds of polygons (with different rotations, scaling factors,...etc.), I use the following code (producing the top picture) modified from 
this answer to this post. The original code ... 
[tikz-pgf]
 

asked by Hany https://tex.stackexchange.com/landing/r/digest?cta=user&id=93617 Score of 5

answered by Qrrbrbirlbel https://tex.stackexchange.com/landing/r/digest?cta=user&id=16595 Score of 7