Are All Triangles Actually Isosceles? Discover My Greek-Euclidean Proof!

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Discussion Overview

The discussion revolves around a claim that all triangles are isosceles, supported by a Greek-Euclidean proof. Participants explore the validity of this assertion and reference historical proofs, particularly one by Lewis Carroll, while analyzing potential errors in reasoning.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant presents a Greek-Euclidean proof claiming that all triangles are isosceles and invites feedback.
  • Another participant questions whether this proof is similar to Lewis Carroll's fallacious proof of the same theorem, suggesting that there may be subtle errors to analyze.
  • A later reply confirms that the Greek phrase used in the proof translates to the Latin "quod erat demonstrandum," indicating a connection to traditional proof closure.
  • Another participant comments on the sketch accompanying the proof, suggesting it cleverly conceals the underlying flaw.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the validity of the proof. There are competing views regarding the nature of the proof and its connection to historical examples, indicating ongoing debate.

Contextual Notes

Participants reference the potential for subtle errors in reasoning and the historical context of similar proofs, but do not resolve these issues or clarify the specific flaws in the presented proof.

Konstantinos88
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That is my Greek-Euclidean proof that all triangles are isosceles. Any doubts?
 

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Is this different from Lewis Carroll's proof of the same "theorem"?

He had a couple of these fallacious proofs, which are a lot of fun to try to analyze. The error is subtle. I won't spoil the fun yet.

Is your last line in Greek the same meaning as the traditional Latin closing "quod erat demonstrandum" (QED)?
 
RPinPA said:
Is your last line in Greek the same meaning as the traditional Latin closing "quod erat demonstrandum" (QED)?

Yes, exactly this: The phrase, quod erat demonstrandum, is a translation into Latin from the Greek ὅπερ ἔδει δεῖξαι (hoper edei deixai; abbreviated as ΟΕΔ).
https://en.wikipedia.org/wiki/Q.E.D.
 
A nice way to draw the sketch to hide the flaw.
 

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