# [pstricks] Defining a maxmum and minimum point

Herbert Voss LaTeX at zedat.fu-berlin.de
Sun Apr 8 18:33:45 CEST 2007

Herbert Voss wrote:
> Arne Hallam wrote:
>
>> So I am going to answer part of my own question.
>>
>> I read a bit more carefully in the PST-3dplot manual and found a couple
>> of pages I had missed.  So I am part of the way there.
>>
>> In the code below I seem to be making a mistake in the definition of the
>> function so that it points down instead of up.  I cannot see anything
>> obvious in my function definition.
>>
>> z= 2(5x +4y -2x^2 +xy -y^2) -6x - 2y
>>
>>
>>
> there was an error in your math expression. Delete the hiddenLine
> option if you do not it.
>
> \documentclass{amsart}
> \usepackage{pstricks,pst-3dplot}
> \pagestyle{empty}
>
> \begin{document}
> $z= 2(5x +4y -2x^2 +xy -y^2) -6x - 2y$
>
> \begin{pspicture*}(-6,-5)(7,10)
> \psplotThreeD[hiddenLine,plotstyle=curve,linecolor=red, drawStyle=xLines,
>     yPlotpoints=20, xPlotpoints=20,linewidth=0.75pt,algebraic](0,4)(0,4){%
>
sorry, should be
\psplotThreeD[hiddenLine,plotstyle=curve,linecolor=red, drawStyle=xLines,
yPlotpoints=20, xPlotpoints=20,linewidth=0.75pt](0,4)(0,4){%

Herbert