Is there any pyramid like that?

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    geometry pyramid
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Discussion Overview

The discussion revolves around the existence of a pyramid with a rectangular base (ABCD) where each edge has different lengths, specifically addressing the condition |AS| + |CS| = |BS| + |DS|. The scope includes geometric reasoning and exploratory approaches to the problem.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions whether the pyramid is meant to be a real structure or a mathematical construct.
  • Another participant suggests that it might be possible to construct such a pyramid but cannot provide an explicit example.
  • A participant notes that Egyptian pyramids do not typically have a rectangular floor plan and clarifies that the unequal edges refer to the non-horizontal edges.
  • One participant proposes visualizing the problem by imagining lifting wires from the corners of the rectangle to a common point, questioning the projection of the tip on the floor.
  • Another participant expresses difficulty in proving the existence of such a pyramid using elementary geometry.
  • One participant suggests starting with a rectangular base and drawing a perpendicular line segment to explore the shape's properties.
  • A participant mentions having tried a similar approach without success in proving the existence of the shape.
  • One participant expresses a belief in the existence of the shape based on an experiment with strings but acknowledges uncertainty about its guarantee.

Areas of Agreement / Disagreement

Participants generally express uncertainty about the existence of the pyramid and the methods to prove it. Multiple competing views and approaches remain, with no consensus reached.

Contextual Notes

Participants note challenges in proving the existence of the pyramid using elementary geometry and the need for clearer definitions or assumptions regarding the edges and their lengths.

karosz
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I had geometry quite a while ago and I wonder if anyone has any idea how to tackle this problem:

Is there any ABCDS pyramid (where ABCD is a rectangle) in which each 2 edges have different lengths and |AS|+|CS|=|BS|+|DS|

Thanks
 
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Do you mean a real pyramid like the ones in Egypt or mathematically?
 
:smile: mathematically. Something tells me one can construct such a pyramid, but I can't give explicit example..
 
No Egyptian pyramids I know of have a rectangular floor plan...

I assume the unequal edges are only the non-horizontal ones (because of this rectangular floor plan) ?

In that case I look at a rectangle on the floor from above; then I imagine two equal length (length > diagonal of rectangle) wires, one from A to C and one from B to D. If I lift them with a hook or something, where can I end up with the top of the pyramid ? Can the projection of the tip on the floor be off both symmetry axes or only off one ?
 
Yes, only non horizontal ones. I tried the same but somehow its hard to show anything "mathematically"
 
You could draw the rectangular base and attach threads to each corner and then pull them up to a common point. This is how I'd visualize it.
 
Me too, I'll try it. But how it can be proven using elementary geometry?
 
I don't know how to prove it other than starting with the rectangular base and drawing a line segment of a any length perpendicular to the base such that one endpoint is in the rectangle then you can draw a line segment from any vertice of the rectangular base to the free line segment endpoint. Something like that...
 
Ive tried that already but it didnt lead me to anywhere
 
  • #10
Are you trying to proof that such a shape exists?
 
  • #11
I firmly believe that it exists - I did an experiment with strings

But I can't guarantee it exists
 

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