9.28.1 Top new questions this week

9.28.1.1 xcolor: How to get the complementary color

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684480

Is there a LaTex-style way to get the complementary color? 
For example, a corresponding command in the xcolor package? 
\documentclass[]{book} 
\usepackage{xcolor} 
\definecolor{Acolor}{named}{red} 
\... 
[color]
 

asked by cis https://tex.stackexchange.com/landing/r/digest?cta=user&id=46023 Score of 8

answered by Rmano https://tex.stackexchange.com/landing/r/digest?cta=user&id=38080 Score of 12

9.28.1.2 Newer versions of LaTeX fail to ignore spaces after display math environments which end with two dollar signs ($$) and contain \eqno

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684207

The LaTeX file 
\documentclass[12pt]{article} 
\begin{document} 
$$ a \eqno 1 $$ 
N\\N 
$$ a \eqno 1 $$% 
N\\N 
\end{document} 
produces an unwanted space after the first displayed equation under "... 
[math-mode]
 

asked by Gabriel A. Lozada https://tex.stackexchange.com/landing/r/digest?cta=user&id=295947 Score of 7

answered by David Carlisle https://tex.stackexchange.com/landing/r/digest?cta=user&id=1090 Score of 10

9.28.1.3 Display system in systeme

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684494

I'm new to the systeme package. I was reading the manual to get to know it, but unfortunately it is written in French. I want to typeset the following 
The best I can come up with is the following ... 
[systeme]
 

asked by Tolaso https://tex.stackexchange.com/landing/r/digest?cta=user&id=71437 Score of 6

answered by Mico https://tex.stackexchange.com/landing/r/digest?cta=user&id=5001 Score of 4

9.28.1.4 Macro for printing monomials

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684466

This is a follow-up to my previous question How to convert a sequence of integers into a monomial 
Question 1. Is it possible a macro that takes two inputs 
varname:   { x1, x2, ... , xn } 
exp:       { ... 
[latex3]
 

asked by underflow https://tex.stackexchange.com/landing/r/digest?cta=user&id=183182 Score of 5

answered by egreg https://tex.stackexchange.com/landing/r/digest?cta=user&id=4427 Score of 3

9.28.1.5 Lindenmayer (L-Systems) colouring individual units

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684307

I use the following code to produce Lindenmayer drawings, utilizing the code from this site. 
Is it possible to modify this code to colour each individual unit with a different colour, producing the ... 
[tikz-pgf]
 

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

answered by Thruston https://tex.stackexchange.com/landing/r/digest?cta=user&id=15036 Score of 8

9.28.1.6 Can I general this code to draw a regular polyhedron?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684305

In this code, I draw a regular polyhedron whose base is an equilateral triangle. 
\documentclass[tikz,border=3mm]{standalone} 
\usepackage{tikz-3dplot} 
\begin{document} 
\tdplotsetmaincoords{70}{... 
[tikz-3dplot]
 

asked by John Paul Peter https://tex.stackexchange.com/landing/r/digest?cta=user&id=250010 Score of 5

answered by Juan CastaA~+-o https://tex.stackexchange.com/landing/r/digest?cta=user&id=231368 Score of 11

9.28.1.7 Is XyMTeX still working for people?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=684320

I am trying to use XyMTeX for typesetting a variety of chemical reactions and keep getting errors, namely with 
\ChemEquation 
\LewisSbond 
\LewistetrahedralA or B 
electron shift arrows and 
Reaction ... 
[chemistry] [xymtex]
 

asked by Cam Lumsden https://tex.stackexchange.com/landing/r/digest?cta=user&id=107583 Score of 5

answered by egreg https://tex.stackexchange.com/landing/r/digest?cta=user&id=4427 Score of 6