Intersect two ellipsoids

SparksMaths shared this question 2 years ago

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The Intersect function appears to accept two quadrics as inputs. When I define two ellipsoids (eq1 and eq2 in the example) the Intersect(eq1,eq2) command returns "undefined". Is this a limitation of the command (it seems to work fine for two spheres) or am I missing something else?

(file attached, or online here: https://www.geogebra.org/m/hsaxzejq)

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mathmagic ● 2 years ago

because your instersection is not a conic

Comments (7)

SparksMaths ● 2 years ago

I can get an intersection to work in the CAS environment, by using Solve({eq1,eq2},{x,y,z})

Still, this occasionally glitches and disappears (e.g. a=1, b=1.8,c=1 f=2, g=1, h=1)

(I wonder if this is for a moment returning a complex value somehow... but not sure why)

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mathmagic ● 2 years ago

https://wiki.geogebra.org/e...

Returns a conic defined in case where the intersection is actually a conic.

https://www.geogebra.org/m/TEERJczX

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SparksMaths ● 2 years ago

Yes - I saw that my intersect command actually got translated into an IntersectConic command. It still returns an undefined...

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mathmagic ● 2 years ago

because your instersection is not a conic

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SparksMaths ● 2 years ago

Agreed. So I can't intersect two objects with the command unless the intersection is a conic?

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mathmagic ● 2 years ago

to show your curves need to render point to point. this is not dynamic. if you want to render the points then Roman´s method can help you

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SparksMaths ● 2 years ago

Understood. Thanks for pointing to the comprehensive methods from Roman. The CAS solution manages to keep it relatively dynamic. Glad to have found both options.

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