MHB Can anyone tell me the real names of these 3D shapes?

[goldieluxe]

I know cylinder, cone and cube, but can't think of the names for the last two. I know this is a very basic question that I should know...but I am blanking. View attachment 6204

 

[MarkFL]

The last two are prisms, a rectangular prism and a right triangular prism.

 

[phymat]

Second last one is precisely known as cuboid and the last one is a triangular prism (as MarkFL said).

 

[Prove It]

Second last one is precisely known as cuboid and the last one is a triangular prism (as MarkFL said).

I don't think there's anything precise with the term "cuboid" as it simply means "cube-like". "Rectangular Prism" is much more specific, as being a 3D shape with all identical rectangular cross-sections...

 

[phymat]

I don't think there's anything precise with the term "cuboid" as it simply means "cube-like". "Rectangular Prism" is much more specific, as being a 3D shape with all identical rectangular cross-sections...

If a name has been given to a 3D shape by ancient mathematicians, why not use it? A square will be called a square, not a rectangle with all sides equal. :)

 

[I like Serena]

If a name has been given to a 3D shape by ancient mathematicians, why not use it? A square will be called a square, not a rectangle with all sides equal. :)

From wiki:

In geometry, a cuboid is a convex polyhedron bounded by six quadrilateral faces, whose polyhedral graph is the same as that of a cube. While mathematical literature refers to any such polyhedron as a cuboid,[1] other sources use "cuboid" to refer to a shape of this type in which each of the faces is a rectangle (and so each pair of adjacent faces meets in a right angle); this more restrictive type of cuboid is also known as a rectangular cuboid, right cuboid, rectangular box, rectangular hexahedron, right rectangular prism, or rectangular parallelepiped.[2]​

So for starters "cuboid" is somewhat ambiguous, and more specifically mathematical literature refers to it without requiring right angles or square faces, while cube and right rectangular prism are well-defined with square respectively rectangular faces.

 

[Prove It]

If a name has been given to a 3D shape by ancient mathematicians, why not use it? A square will be called a square, not a rectangle with all sides equal. :)

Ancient mathematicians also believed that all numbers were rational and killed anyone who could prove otherwise. Yes, why not use their logic?

 

[phymat]

From wiki:

In geometry, a cuboid is a convex polyhedron bounded by six quadrilateral faces, whose polyhedral graph is the same as that of a cube. While mathematical literature refers to any such polyhedron as a cuboid,[1] other sources use "cuboid" to refer to a shape of this type in which each of the faces is a rectangle (and so each pair of adjacent faces meets in a right angle); this more restrictive type of cuboid is also known as a rectangular cuboid, right cuboid, rectangular box, rectangular hexahedron, right rectangular prism, or rectangular parallelepiped.[2]​

So for starters "cuboid" is somewhat ambiguous, and more specifically mathematical literature refers to it without requiring right angles or square faces, while cube and right rectangular prism are well-defined with square respectively rectangular faces.

Does the diagram posted by OP specify right angles or square faces?
Also, how would you define a cuboid?

 

[I like Serena]

Does the diagram posted by OP specify right angles or square faces?
Also, how would you define a cuboid?

Examples of cuboids... I think they look different from what is shown in the OP...

View attachment 6366

 

[phymat]

Examples of cuboids... I think they look different from what is shown in the OP...

They 'look' different, but it is nowhere specified in the original diagram by OP that all angles are right angles and 4 faces are rectangular. Since it is not specified, cuboid is the most appropriate name for the shape. In a case that it had been specified, it could have been called as rectangular cuboid.