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par-projectioncercle-en.tex
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par-projectioncercle-en.tex
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\section{Circles}
\subsection{Direct definition}
The object \Lkeyword{cercle} allows us to define and draw a \Index{circle}.
In the \texttt{pst-solides3d} package, a circle in 2D is defined
by its centre and radius.
We use the option \Lkeyword{args} to specify the centre and radius of
the chosen circle. We can use coordinates or named variables.
The argument \texttt{\Lkeyword{range}=$t_{\rm min}$ $t_{\rm max}$} allows %$
us to specify an arc of the chosen circle.
As for all the other object, we can save the circle data using the
option \Lkeyword{name}.
\begin{LTXexample}[width=7.5cm]
\begin{pspicture}(-3,-3)(4,3.5)%
\psframe*[linecolor=blue!50](-3,-3)(4,3.5)
\psset{viewpoint=50 30 15,Decran=60}
\psset{solidmemory}
%% definition du plan de projection
\psSolid[object=plan,
definition=equation,
args={[1 0 0 0] 90},
planmarks,
name=monplan]
\psset{plan=monplan}
%% definition du point A
\psProjection[object=point,
name=A,
text=A,
pos=ur](-2,1.25)
\psProjection[object=cercle,
args=A 1,
range=0 360]
\psProjection[object=cercle,
args=1 1 .5,linecolor=blue,
range=0 180]
\composeSolid
\end{pspicture}
\end{LTXexample}
\subsection{Some other definitions}
There are additional methods to define a circle in 2D. The options
\Lkeyword{definition} and \Lkeyword{args} give the following supported
methods:
\begin{itemize}
\item \texttt{\Lkeyword{definition}=\Lkeyword{ABcercle}};
\texttt{\Lkeyword{args}=$A$ $B$ $C$}.
A circle through the points $A$, $B$
and $C$.
\item \texttt{\Lkeyword{definition}=\Lkeyword{diamcercle}};
\texttt{\Lkeyword{args}=$A$ $B$}.
A circle with diameter $[AB]$.
\end{itemize}
\endinput

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