sequence gives different result than individual terms in sequence

Lenore shared this problem 1 month ago
New

I'm trying to show horizontal traces and contours of 2D surfaces. The horizontal traces work fine but the contours are not working well.


sequence(f=c,cmin,cmax,dc)
produces no results for some functions (-xye^(-x^2-y^2) for instance).

Sequence(Translate(IntersectPath(z = c, a), Vector((0, 0, -c))), c, cmin, cmax, dc)
and related things zipping the list of horizontal traces with the list of plane heights that created the traces all produce curves entirely unrelated to the horizontal traces (and blatantly incorrect contours for the function). The only thing that works is tying translation of the intersection curves to a slider and then tracing that.


Warning, because I tried to show various methods all in one file, the file is enormously taxing to the CPU and nearly as slow as pouring molasses outside in the arctic winter.


Tried both GeoGebra 5.0.620.0 and GeoGebra 6.0.620 on MacBook Air running MacOS 10.14.6.

Comments (4)

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IntersectPath( <Plane>, <Quadric> )


won't work for non-quadrics

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"Michael Borcherds

IntersectPath( <Plane>, <Quadric> )


won't work for non-quadrics

"


Curious because the intersection actually works. So does translating it down to the xy plane. All that doesn't work is translating to the xy plane as a sequence. See attached.

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f=z ; z=c <==> c=f

Files: foro.ggb
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"mathmagicf=z ; z=c <==> c=f

"

Yes. That is the goal. But intersecting the object and the plane works whereas setting z=f directly does not. Presumably a different behind the scenes approach is being used where in one case parametric curves can be found and in the other they cannot.

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