Listing symmetries geometrically and analytically, what do I do?

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Discussion Overview

The discussion revolves around identifying and listing the symmetries of a double square pyramid defined by specific vertex coordinates. Participants are tasked with describing these symmetries both geometrically and analytically, exploring various transformations and their implications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant expresses uncertainty about how to begin solving the problem of listing symmetries for the double square pyramid.
  • Another participant provides hints suggesting that the points E and F, being closer to the origin, either remain fixed or are swapped by symmetries, and notes that symmetries act on the vertices A, B, C, and D entirely in the xy-plane.
  • A participant outlines several rotations (90 degrees, 180 degrees, 270 degrees) and reflections (through planes involving points E and F, and through the plane containing A, B, C, and D) as potential symmetries.
  • There is a suggestion to compose all rotations with all reflections to obtain a complete list of symmetries.
  • Another participant challenges the assumption that E and F determine a plane, stating they are merely two points, and introduces the idea of considering symmetries as a subgroup of S2 x S4, noting that there are 16 distinct symmetries.
  • A later reply questions whether reflection 1 can be considered a reflection through the origin.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the symmetries, particularly regarding the role of points E and F and the total count of distinct symmetries. The discussion remains unresolved with multiple competing perspectives on the problem.

Contextual Notes

There are limitations regarding the definitions and assumptions about the symmetries, particularly concerning the treatment of points E and F and the implications of reflections and rotations in the context of the given geometry.

JohnMcBetty
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I have found this question and not sure where to begin in terms of solving it. PLEASE HELP!

Consider a double square pyramid . Introduce a coordinate P system so that the
vertices of P are:

A=(2,0,0)
B=(0,2,0)
C=(-2,0,0)
D=(0,-2,0)
E=(0,0,1)
F=(0,0,-1)

List the symmetries of P. Do this both geometrically and analytically.
 
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hint number 1: E and F are closer to the origin than the other vertices. so they either remain fixed by a symmetry, or swapped.

hint number 2: by hint number 1, all symmetries act on A,B,C and D entirely in the xy-plane. A,B,C and D form a square.
 
Thanks Deveno!

Ok so far this is what I have.

If we rotate the plane containing A,B,C,D

Rotation 1, 90 degrees = A maps to B maps to C maps to D maps back to A
Rotation 2, 180 degrees = A maps to C back to A again, and B maps to D and back to B.
Rotation 3, 270 degrees = A maps to D maps to C maps to B maps back to A
Rotation 4 would just be our initial point (epsilon)

Reflection 1, through plane containing E and F, A maps to D and back to A. B maps to C and back again.
Reflection 2, through the plane containing A,B,C, and D, E maps to F and maps back to E.

I would then compose all of the rotations with all reflections

Would this be all I would have to do? Better question, did I solve this problem in a correct manner?
 
Thanks Deveno!

Ok so far this is what I have.

If we rotate the plane containing A,B,C,D

Rotation 1, 90 degrees = A maps to B maps to C maps to D maps back to A
Rotation 2, 180 degrees = A maps to C back to A again, and B maps to D and back to B.
Rotation 3, 270 degrees = A maps to D maps to C maps to B maps back to A
Rotation 4 would just be our initial point (epsilon)

Reflection 1, through plane containing E and F, A maps to D and back to A. B maps to C and back again.
Reflection 2, through the plane containing A,B,C, and D, E maps to F and maps back to E.

I would then compose all of the rotations with all reflections

Would this be all I would have to do? Better question, did I solve this problem in a correct manner?
 
E and F don't determine a plane, they are only two points.

you can regard these symmetries as a subgroup of S2 x S4, since the reflection through the xy-plane doesn't change A,B,C or D, and the rotations in the xy-plane and the reflections in the xy-plane don't change E or F (that is, swapping E and F commutes with all operations that only affect the xy-plane).

i count 16 distinct symmetries in all (the subgroup corresponding to the subgroup of S4 isn't all that big, we can't allow "twisted" mappings of vertices).
 
So should I just say that reflection 1 is a reflection through the origin?
 

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