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Salve. Quod erat demonstrandum (Q.E.D.). This Latin phrase means "what was to be demonstrated." It's used at the end of a proof or argument to show that what...
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The phrase quod erat demonstrandum is a translation into Latin from the Greek ὅπερ ἔδει δεῖξαι (hoper edei deixai; abbreviated as ΟΕΔ). The meaning of the Latin phrase is "that [thing] which was to be demonstrated" (with demonstrandum in the gerundive).
In mid-1980s Romania, the Securitate investigate a gifted mathematician when it comes comes to their attention that he has secretly arranged for an academic paper on his new theorem to be ...
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It was invented by Aristotle (384–322 B.C.) in Athens, and recorded in a group of writings known as the Organon. In one of these works, the Prior Analytics, Aristotle attempted to provide a complete analysis of the valid forms of reasoning.
Euclid used the Greek original of Quod Erat Faciendum (Q.E.F.) to close propositions that were not proofs of theorems, but constructions of geometric objects. For example, Euclid's first proposition showing how to construct an equilateral triangle , given one side, is concluded this way.
The earliest known use of the phrase quod erat demonstrandum is in the early 1600s. OED's earliest evidence for quod erat demonstrandum is from 1614, in the writing of William Bedwell, Arabist and mathematician.
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These initials stand for the Latin quod erat demonstrandum meaning, ‘what was to be demonstrated’. It was coined by Euclid in Greek c. 300 BC but it is better known in its Latin translation. The expression QED is typically used by mathematicians and philosophers to conclude proofs and arguments.
