[pstricks] tangent to \psellipse or \pscircle
Juergen Gilg
gilg at acrotex.net
Tue Oct 30 08:22:39 CET 2007
Dear Patrick,
here a more PS-tricky solution
\documentclass{article}
\usepackage{pstricks,pst-plot,pstricks-add}
\begin{document}
\begin{pspicture}(-4.5,-4.5)(4.5,4.5)
\psaxes{->}(0,0)(-4.5,-4.5)(4.5,4.5)
\psplot[algebraic,plotpoints=500]{-4}{4}{(16-x^2)^(0.5)}
\psplot[algebraic,plotpoints=500]{-4}{4}{-(16-x^2)^(0.5)}
\psplotTangent[algebraic,linecolor=blue]{3}{1}{(16-x^2)^(0.5)}
\end{pspicture}
alternative
\begin{pspicture}(-4.5,-4.5)(4.5,4.5)
\psaxes{->}(0,0)(-4.5,-4.5)(4.5,4.5)
\psplot[polarplot,algebraic,plotpoints=500]{0}{TwoPi}{4}
\psplotTangent[polarplot,algebraic,linecolor=blue]{Pi}{1}{4}
\end{pspicture}
\end{document}
Regards,
Juergen
Patrick Drechsler wrote:
> Patrick Drechsler <patrick at pdrechsler.de> writes:
>
>
>> what is the best way to draw a tangent to \psellipse or \pscircle at
>> certain coordinates? And how does one retreive these coordinates?
>>
>
> Using pst-eucl solved the problem at hand.
>
> For the record:
>
> --8<---------------cut here---------------start------------->8---
> \documentclass{article}
> \usepackage{pstricks}
> \usepackage{pst-eucl}
> \usepackage{pstricks-add}% needed for \psRelLine
> \SpecialCoor%
> \begin{document}
> \begin{pspicture}[showgrid=true](-3,-3)(2.5,2)
> %% Circle:
> \pstGeonode(0,0){O}%
> \pstGeonode(2,0){A}%
> \pstCircleOA{O}{A}% draw circle
> %% Line:
> \pstGeonode[PosAngle=135](-2,-1.5){W1}%
> \pstGeonode[PosAngle=135](3,-1.5){W2}%
> \psline[linewidth=0.5pt,linecolor=gray](W1)(W2)% draw line
> %% Intersection between line and circle:
> \pstInterLC[PosAngleA=-90,PosAngleB=-45]{W1}{W2}{O}{A}{SP1}{SP2}
> %% Secant between the above intersection points SP1 and SP2:
> \psline[linecolor=blue](SP1)(SP2)
> %% Draw radius:
> \psline[linecolor=cyan](O)(SP1)
> %% Tangent:
> \psRelLine[linecolor=red,angle=90](SP1)(O){0.5}{EndnodeA}
> \psRelLine[linecolor=red,angle=-90](SP1)(O){0.5}{EndnodeB}
> \rput([offset=-.3]EndnodeB){{\color{red}tangent}}
> \end{pspicture}
> \end{document}
> --8<---------------cut here---------------end--------------->8---
>
> There are probably more elegant ways of doing this.
>
> Cheers,
>
> Patrick
>
--
jürgen gilg
austr. 59
70376 stuttgart
tel 0711-59 27 88
e-mail gilg at acrotex.net
website www.acrotex.net
www.gilligan-online.de
www.brueckenkurs-physik.de
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