Hi Autumn,
welcome to the forum!
Look at the line for coordinate A here, I put the semicolon at the end. It is missing in your original code. Every TikZ path has to end with a semicolon.
Code: Select all
%!TEX lualatex
\documentclass{ltjsarticle}
\usepackage{tikz}
\usetikzlibrary{intersections,calc,arrows.meta}
\begin{document}
\begin{tikzpicture}
\coordinate[label=left:A](A)at(0,0);
\coordinate[label=right:B](B)at(3,0);
\coordinate[label=above:C](C)at(2,2);
\draw(A)--(B)--(C)--cycle;
\end{tikzpicture}
\end{document}
You can click on "Run LaTeX here" to see that it works.
By the way, I removed the
dvipdfmx
option, which is not compatible with LuaLaTeX, required by
ltjsarticle
.
To 2. you accidentally used the "LaTeX" button, which is for inline code marking of LaTeX commands. For multiple lines of code, there's the "Code" button at the left top of the editor field when writing. Not perfect, I guess. I edited it above.
Stefan