Because that is how a polyhedron is defined.
Polyhedrons can only have straight sides.
A triangle is not a polyhedron. A triangle is a two-dimensional figure, and a polyhedron is a three-dimensional solid. An example of a triangular-shaped polyhedron is a pyramid.
Cube, parallelogram, and prism
No. A polygon is a 2-dimensional figure. A polyhedron is 3-dimensional.
cylinder
A polyhedron is a three-dimensional figure formed by flat surfaces that are bounded by polygons joining along their sides (the faces of the polyhedron).A circle is not a polygon, but we can say that a circle is the limit of a regular polygon with n sides. It means that if n becomes larger and larger, the polygon shape approaches to a circle. A circle is a two dimensional figure as a polygon is, but a three dimensional figure whose base(s) is/are a circle cannot be called a polyhedron.
Because that is how a polyhedron is defined.
Because that is how a polyhedron is defined.
A polyhedron.
It is so by definition.
Sphere
cube
312
A triangle is not a polyhedron. A triangle is a two-dimensional figure, and a polyhedron is a three-dimensional solid. An example of a triangular-shaped polyhedron is a pyramid.
Cube, parallelogram, and prism
It is a sphere which looks like a globe
No. A polygon is a 2-dimensional figure. A polyhedron is 3-dimensional.
A polyhedron is a closed figure with several (planar) sides, and all its sides are planar. A non polyhedron does not have these properties, maybe it is not closed, maybe one or more of the sides is a curved surface. In some branches of topology the sides of a polyhedron cannot intersect each other.