Take the 2-minute tour ×
TeX - LaTeX Stack Exchange is a question and answer site for users of TeX, LaTeX, ConTeXt, and related typesetting systems. It's 100% free, no registration required.

I used Geogebra to draw the graph of the function $y = 2x^2 - 4x$. This is my code

\documentclass[10pt]{article}
\usepackage{pstricks-add}
\pagestyle{empty}
\begin{document}
\psset{xunit=1.0cm,yunit=1.0cm,algebraic=true,dotstyle=o,dotsize=3pt 0,linewidth=0.8pt,arrowsize=3pt 2,arrowinset=0.25}
\begin{pspicture*}(-2,-2.44)(3.92,5)
\psaxes[labelFontSize=\scriptstyle,xAxis=true,yAxis=true,Dx=1,Dy=1,ticksize=-2pt 0,subticks=2]{->}(0,0)(-2,-2.44)(3.92,5)[,140] [y,-40]
\psplot[linewidth=1.6pt,plotpoints=200]{-2.0}{3.9165217391304363}{2*x²-4*x}
\psline[linewidth=1.6pt,linestyle=dashed,dash=3pt 3pt](1,-2)(1,0)
\psline[linewidth=1.6pt,linestyle=dashed,dash=2pt 2pt](1,-2)(0,-2)
\begin{scriptsize}
\psdots[dotstyle=*,linecolor=blue](1,-2)
\rput[bl](1.02,-1.93){\blue{$A$}}
\psdots[dotstyle=*,linecolor=blue](1,0)
\rput[bl](1.02,0.08){\blue{$B$}}
\psdots[dotstyle=*,linecolor=blue](0,-2)
\rput[bl](0.02,-1.93){\blue{$C$}}
\end{scriptsize}
\end{pspicture*}
\end{document}

I use Texmaker and compiler with keys F2 -> F4 ->F8 ->F7. But I got enter image description here

How can I get correct picture?

share|improve this question
add comment

2 Answers

up vote 5 down vote accepted

the function is not correct:

\psplot[linewidth=1.6pt,plotpoints=200]{-2.0}{3.9165217391304363}{2*x^2-4*x}

you have {2*x²-4*x}. An exponent must be written as x^2

However, the export of GeoGebra is not really nice. Use:

\documentclass[10pt]{article}
\usepackage{pstricks-add}
\pagestyle{empty}
\begin{document}

\psset{algebraic,linewidth=0.8pt,arrowsize=3pt 2,arrowinset=0.25}
\begin{pspicture*}(-2,-2.44)(3.92,5)
\psaxes[labelFontSize=\scriptstyle,ticksize=-2pt 0,subticks=2]{->}(0,0)(-2,-2.44)(3.92,5)[,140] [y,-40]
\psplot[linewidth=1.6pt,plotpoints=200]{-2.0}{3.9165217391304363}{2*x^2-4*x}
\psCoordinates[linecolor=blue,linestyle=dashed](1,-2)
\psdots[dotstyle=*,linecolor=blue](1,0)(0,-2)
\scriptsize
\rput[bl](1.02,-1.93){\blue{$A$}}
\rput[bl](1.02,0.08){\blue{$B$}}
\rput[bl](0.02,-1.93){\blue{$C$}}
\end{pspicture*}

\end{document}

enter image description here

share|improve this answer
add comment

A recommended solution for best practitioners.

\documentclass[pstricks,border=12pt,12pt]{standalone}
\usepackage{pst-plot}
\usepackage{pst-eucl}

\psset
{
    algebraic,
    arrowsize=3pt 2,
    arrowinset=0.25,
    plotpoints=200,
    saveNodeCoors,
}

\def\func(#1){2*(#1)^2-4*(#1)}

\begin{document}
\begin{pspicture}(-2,-2.5)(4,5)
\psplot[linecolor=red,yMaxValue=4]{-2.0}{4}{\func(x)}
\psaxes[labelFontSize=\scriptstyle,ticksize=-4pt 0,subticks=2,linecolor=lightgray]{->}(0,0)(-2,-2.5)(3.5,4.5)[$x$,0][$y$,90]
\everypsbox{\scriptsize\color{blue}}
\pstGeonode[linecolor=blue,PosAngle={90,-90,-135}](1,0){B}(*N-B.x {\func(x)}){A}(0,|A){C}
\psline[linestyle=dashed,linecolor=blue](B)(A)(C)
\end{pspicture}
\end{document}

enter image description here

Edit

I just knew by a trial and error that (x,y|P) can be simplified as (x,|P). And its dual, (P|x,y) can be simplified as (P|,y). I don't know whether it is a useful bug or a by-design feature.

Be careful, the yMaxValue apparently depends on plotpoints. A pessimistic approach is to use a large plotpoints (for example 5000) to make a better resolution, but the file size becomes bigger. :-)

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.