Elliptic curves, points, zooming

Ed Lazda shared this problem 1 year ago
Not a Problem

Hi

I've noticed a problem. I plotted the elliptic curve y^2 = x^3 - x + 1 and added a point P. When I zoom in and out, P moves along the curve. I've tried fixing the object but it still happens. It's the same if I use the mouse or the on-screen zoom buttons.

It doesn't happen with parabolas y=x^2 or y^2=x.

I'm using classic Geogebra v6 on Linux. The same thing happens when using the online version in Chrome browser.

I don't remember this problem last time I plotted some elliptic curves a few weeks back, but I could have overlooked it then.

Thansks

Ed

Comments (6)

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I confirm in ver5.0.445 windows7

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Sorry, that's expected

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That's interesting and unexpected -- to me anyway :-) . It makes it difficult to play around with the groups arising from elliptic curves. What is the advantage in having that happen?

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Hi,

workaround :

see in script of Uptdate of point C_1

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Can you explain the workaround? Why do I need C_1? Thanks in advance.

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When using the workaround the points look stable. But when I zoom out a lot the points are not stable anymore. And when I use a elliptic curve with two branches (f.e. y^2=x^3-x) than the points P and PP will swap from one branch to the other branch.

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