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.

Yes, it has three corners and three edges. It is a triangle.

What if it had 3 corners and 4 edges? Or 4 corners and 3 edges?

If a shape has 3 corners and 4 edges, it is incomplete or open and therefore not a shape yet but a collection of edges (or possibly, two triangles that share an edge).

A shape with 4 corners and 3 edges is not possible. An edge cannot have a corner in the middle of it, that would make it two edges.

I felt like adding something about the specific case of 180° between edges and a vertice.

Makes sense.

And I guess too many vertices means an open set of edges (ie not close, this not a shape).

I was kinda hoping for a strange edge case, like a mobius strip or Klein bottle.

I guess a mobius strip is a 2d representation of a 1d paradigm. And a klein bottle is a 3d representation of a 2d paradigm.

It would be too much to ask of a 1d representation of a ??d paradigm.

Why the down votes? Bro asking a question and being legit curious, don’t be hating on someone that’s looking to challenge what they know just because it’s trivial to you.

I feel my comment adds to the discussion and wants more details.

But it was too simply phrased.

I guess the details of such a question should be obvious. And if you need the details, the question doesn’t actually add the the discussion… It just seems idiotic!

I felt like there might be a really cool scenario where a vertice isn’t considered a vertice.

Like, there actually might be some case on a 2d plane “where actually” applies.

I’m fine being wrong

Welcome to Lemmy, first time?

I don’t think that can be a thing.

Yeh, seems not

It doesn’t matter that the edges are curved?

If you were to walk this route along the surface of the earth, you would walk in perfectly straight lines apart from the three turns.

No such thing. Even if you were walking on a surface with no change in elevation, the acceleration due to gravity would cause your path to be curved as it followed the curvature of the planet.

Curved relative to what?

Edit: Nvm, I understood what you mean. But I think it’s a pedantic take. They obviously mean it in the context of the surface of the sphere.

They’re not curved; the space they’re embedded in is curved.

The space itself has canonical curvature >.>

Well that depends on your definition of curved… If I look at this image from a 3 dimensional coordinate system that includes the sphere, the edges are definitely curved. Of course, if you look at this from the coordinate system “surface of the sphere” then I would agree with you. There are 2 ways to look at this and decide if it is a triangle, and the bro you responded to didn’t understand this and needs it explained.

I don’t think this is relevant. Using your first definition there is no possible way to walk in a straight line on a sphere. While true in that context I don’t think it’s what most people are meaning by “straight line”.

But it’s absolutely clear that the first definition is meant by the person that is being responded to. That is why the clarification is needed. This is not about “most people”, but this specific one person in this specific comment thread. “It doesn’t matter that the edges are curved?” is only said by someone that thinks in the first definition, not in the second.

The edges curve in 3d space, but not relative to the sphere.