Proof by contradiction is a powerful tool.
Father of geometry
While Euclid extensively used proof by contradiction (reductio ad absurdum) throughout 'Elements', this specific phrasing is a modern summary of his method, not a direct quote.
c. 300 BCE (implied by method)
Found in 1 providers: grok
Cross Reference
1 source
"A point is that which has no part."
Strange & Unusual"A line is breadthless length."
Strange & Unusual"Let it be granted that all right angles are equal to one another."
Strange & Unusual"If equals be subtracted from equals, the remainders are equal."
Strange & Unusual"Parallelograms which are on the same base and in the same parallels are equal to one another."
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