Is this a triangle?

november@lemmy.vg to No Stupid Questions@lemmy.world – 173 points –

I would have asked this on a math community but I couldn't find an active one.

In a spherical geometry, great circles are "straight lines". As such, a triangle can have two or even three right angles to it.

But what if you go the long way around the back of the sphere? Is that still a triangle?

(Edit:) I guess it's a triangle! Fair enough; I can't think of what else you would call it. Thanks, everyone.

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Would the southern shape here also qualify as a triangle?

What if you went the short way instead of the long way, creating the spherical triangle people usually use - then is the "outside" portion of the triangle itself another triangle?

Yes, that would be a different triangle. If you have 3 points on a sphere, there are multiple triangles that contain them as vertices.

I didn't even think of that. Another good question!

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