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.

      • RightHandOfIkaros@lemmy.world
        link
        fedilink
        English
        arrow-up
        21
        ·
        edit-2
        2 months ago

        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.

        • towerful@programming.dev
          link
          fedilink
          arrow-up
          2
          ·
          2 months ago

          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.

      • ByteJunk@lemmy.world
        link
        fedilink
        arrow-up
        5
        ·
        2 months ago

        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.

        • towerful@programming.dev
          link
          fedilink
          arrow-up
          4
          ·
          2 months ago

          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

      • bionicjoey@lemmy.ca
        link
        fedilink
        arrow-up
        10
        ·
        2 months ago

        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.

        • I_Has_A_Hat@lemmy.world
          link
          fedilink
          arrow-up
          1
          arrow-down
          4
          ·
          2 months ago

          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.

          • Farid@startrek.website
            link
            fedilink
            arrow-up
            9
            ·
            edit-2
            2 months ago

            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.

      • november@lemmy.vgOP
        link
        fedilink
        English
        arrow-up
        7
        arrow-down
        2
        ·
        2 months ago

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

        • Azzu@lemm.ee
          link
          fedilink
          arrow-up
          1
          ·
          edit-2
          2 months ago

          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.