Well, any shape with a triangular face.
I assume that you mean a shape that only has (identical) triangles for faces.
There are 2: the tetrahedron with 4 triangles, and the icosahedron with 20 triangles.
* * * * *
What about a triangular dipyramid? Two triangular pyramids stuck together along one face?
If you have one flat face and I have one curved face, which one of us is the 3d shape? Anyway, a 3d shape with pne f;at, circular face and one curved face could be: a section of a sphere or a section of an ellipsoid cut by a plane parallel to one of its axes, a section of a paraboloid or a cone. There are probably other shapes.
A cylinder !
A cone.
Hemisphere
sphere
sphere
A sphere
A blob.
If you have one flat face and I have one curved face, which one of us is the 3d shape? Anyway, a 3d shape with pne f;at, circular face and one curved face could be: a section of a sphere or a section of an ellipsoid cut by a plane parallel to one of its axes, a section of a paraboloid or a cone. There are probably other shapes.
A cylinder !
A cone.
Mobius strip
An edge.
A cone
hemisphere
They both have a face, not a :) face but a side of a shape is called a face and a 2d and 3d shape both show a face of the shape
Hemisphere