Group of Symmetry of Rectangle: Reflections & Diagonals

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Discussion Overview

The discussion centers on the group of symmetries of a rectangle, particularly focusing on the nature of reflections and rotations. Participants explore why a rectangle has only two reflection symmetries compared to a square, and the implications of reflecting a rectangle over its diagonals.

Discussion Character

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

Main Points Raised

  • One participant questions why the group of symmetries of a rectangle includes only two reflections and not reflections over the diagonals, as is the case with squares.
  • Another participant inquires about the outcome of reflecting a rectangle with unequal side lengths across one of its diagonals.
  • A participant suggests that reflecting the rectangle results in the longer side changing orientation, indicating a transformation of its position.
  • There is a mention that rotation by 180 degrees is also a symmetry of the rectangle, prompting further questions about the differences between rotation and reflection.
  • Some participants express uncertainty about the implications of these transformations and the concept of symmetry in relation to orientation.

Areas of Agreement / Disagreement

Participants express differing views on the nature of reflections and rotations in relation to the rectangle's symmetry. There is no consensus on the reasons behind the limited reflections or the effects of diagonal reflections.

Contextual Notes

Participants reference external resources for visual aids, indicating that understanding may depend on specific definitions and interpretations of symmetry. The discussion does not resolve the mathematical or conceptual uncertainties raised.

Who May Find This Useful

This discussion may be of interest to individuals studying geometry, particularly those exploring symmetry, transformations, and the properties of shapes like rectangles and squares.

LagrangeEuler
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What happens if you reflect a rectangle with two different side lengths at one of its diagonal?
 
They change sides I suppose. So when I did that transformation longer side if it was horizontal it will be vertical after that transformation. Right?
 
Yes. If it was first lying down, the it's standing up afterwards, so it changed. This doesn't happen if you reflect it along the half sections parallel to the borders. By the way, rotation also makes a difference, even if rotated by ##180°##. Do you know why?
 
Have you tried these physically with a piece of paper?
 
LagrangeEuler said:
I don't not why
http://mathonline.wikidot.com/the-group-of-symmetries-of-a-rectangle
If I look figure here rotation by 180 degrees will be symmetry.
Yes, that's true. But what happens if you add an orientation, a tiny arrow which shows a direction you could walk along the rectangle? Then you see, that rotation and reflection are different, although the non-oriented figure is the same. (Not important to your original question though, but useful to remember.)
 
Thanks a lot Sir for your help.
 
Last edited:

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