6

It is easy enough to implement using \pgfpatharcaxes and \pgfpointpolarxy.

\documentclass{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
  \draw[red] (0,0) arc[x radius=2, y radius=1, rotate=-45,
    start angle=0, end angle=180];

  \pgfpathmoveto{\pgfpointorigin}
  \pgfpatharcaxes{0}{180}{\pgfpointpolarxy{-45}{2}}%
    {\pgfpointpolarxy{-45+90}{1}}
  \pgfusepath{draw}
\end{tikzpicture}
\end{document}

demo

John Kormylo
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    Give it to \draw as an option – percusse Jan 17 '18 at 16:34
  • @percusse - I was trying to use it with \clip (see https://tex.stackexchange.com/questions/408245/clipping-more-complicated-shapes-in-tikz/410379#410379). – John Kormylo Jan 17 '18 at 16:36
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    You can also add [rotate=-45] just before arc[...]: \draw[red] (0,0) [rotate=-45] arc[x radius=2, y radius=1, start angle=0, end angle=180];. – Paul Gaborit Jan 17 '18 at 16:48
  • @PaulGaborit - I wasn't aware the TikZ parser could do that. Would you like to submit that as an answer to close the question? – John Kormylo Jan 17 '18 at 16:50
  • @JohnKormylo See p.146, pgfmanual, v3.0.1a: At any point where TikZ expects a path operation, you can also give some graphic options, which is a list of options in brackets... – Paul Gaborit Jan 17 '18 at 16:58
  • One could use the same protocol to implement rotate with circle, BUT YOU DON'T HAVE TO! – John Kormylo Jan 19 '18 at 15:26

1 Answers1

6

TikZ arc uses PGF \pgfpatharc and it doesn't have flexibility in adding transformations.

Instead you can add a inline scope 

\begin{tikzpicture}
\draw[red] (0,0) --(1,1) {[rotate=-45] arc[x radius=2, y radius=1, start angle=0,
           end angle=180] -- (-1,1)} -- (-1,1) -- cycle;
\end{tikzpicture}

enter image description here

percusse
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