Talk:Prism (geometry)

message: current article (quote):"Take a polygon with n vertices, n edges. Its prism has 2n vertices, 3n edges, and 2 + n faces. Take a polyhedron with v vertices, e edges, and f faces. Its prism has 2v vertices, 2e + v edges, 2f + e faces, and 2 + f cells. Take a polychoron with v vertices, e edges, f faces and c cells. Its prism has 2v vertices, 2e + v edges, 2f + e faces, and 2c + f cells, and 2 + c hypercells."
:I suggest "Take a polygon, polyhedron, or polychoron and sum the number of vertices w/ number edges, and number of faces,and,..,number of polychorons(=1). If one takes the prism of the original object, the corresponding sum is 3 times larger." I don't have a citation for this theorem, but it's easy to prove from the above formulae, and there aren't citations for those formulae either.-Rich Peterson75.45.106.99 (talk) 22:51, 6 June 2009 (UTC)
replies: text: I should have said that this along with the formulas, not formulae, already there would provide nice setting for the Pascal's triangle method of counting vertices edges etc on an n-cube:Just go to the nth row of triangle for 1+2x.(I know this method used to be on Wikipedia but I can't find it now.)Best wishes, Rich Peterson75.45.106.99 (talk) 23:04, 6 June 2009 (UTC)
thread_title: I suggest one more good formula

message: If you slice a cylinder lengthways along its axis you get two shapes that have many of the properties of a prism, but are not prisms by the current definition.  The solid has one flat face and one that is curved.  It's volume is the area of the end face times it's length and its surface area can be found in the same way as a prism.  But its not a prism and its not a cylinder.  What is to stop this being considered a prism?  (Aside from the obvious fact that the current definition exludes it by requiring polygonal faces).
Perhaps a prism could be "A solid with two congruent parallel faces, and where any cross section parallel to those faces is congruent to them."  Thoughts?
: The shape you are describing is a right semicircular cylinder, half of a right circular cylinder.
: In the same way that "A cone with a polygonal base is called a pyramid.", a cylinder with two polygonal bases is called a prism. --DavidCary (talk) 17:50, 10 October 2020 (UTC)
thread_title: Do prism really have to have polygonal faces?

message: The previous text had been: 
:: In geometry, an n-sided prism is a polyhedron made of an n-sided polygonal base, a translated copy, and n faces joining corresponding sides. 
People reading that had found it confusing, largely because of the ambiguous use of "side": n-sided prism uses "side" to refer to (lateral) faces, while "n-sided polygon" uses "side" to refer to edges. The sense of "side" as "face" got the readers to ask "shouldn't a prism with an n-sided base have n + 2 sides (faces)?" I took the original intent of "an n-sided prism" to be an attempt to explain the nomenclature so, after clarifying the initial definition, I added the sentence about naming at the end.
The entry under faces in the table, too, was confusing because something like "p + 2" was expected, corresponding to the 2p and 3p in the vertices and edges entries, but that may just have been the result of the confusion set up by the initial paragraph, so I left it alone.  An alternative --- p + 2 (two p-gons as bases and p parallelograms as lateral faces) --- would be clearer, but longer. PGoldenberg (talk) 13:49, 30 September 2010 (UTC)
replies: text: One also can't count on a casual reader to understand translated. —Tamfang (talk) 01:31, 1 October 2010 (UTC)
thread_title:  Why the edit to the lead paragraph? 

message: The claim made in this article that the Azrieli Towers are prism (sic) is incorrect. A cylinder is not a prism, and those buildings include a cylinder, therefore the statement is incorrect. The fact that cylinders can be approximated by prims is irrelevant to this fact.  Aparently the claim was made by a non-existent user, Ace-af 
Moreover, the inclusion in this article of an image of these buildings is misleading and confusing given that only two of them are prisms, and one is not. One of my students was in fact confused by this image.
I hope the usual maintainer of this page can fix these issues. I am not proficient in using wikipedia hypertags. Thanks!  — Preceding unsigned comment added by c-67-175-215-221.hsd1.il.comcast.net (talk) 07:37, 23 August 2013 (UTC)
thread_title:  Claim that ''Azrieli Towers are prism'' is incorrect. 

message: Where is the inconsistency in Euclid's definition of a prism? How is a triangular-based prism in conflict with it?  — Preceding unsigned comment added by 92.0.106.148 (talk) 18:37, 16 October 2020 (UTC)
replies: text: There is no inconsistency. Whoever wrote that paragraph was synthesizing from the comments of two older works, both of which mention that they hold minority opinions. I would not consider those older works to be reliable sources, but I'll rewrite that paragraph to mention the opposing views.--Bill Cherowitzo  (talk) 20:43, 16 October 2020 (UTC)
thread_title:  Euclid's inconsistency