Monday, July 26, 2010

Not Quite Easily Done (QED)

I was showing Sean an algebraic solution to a math question, and at the end of it, right next to the answer, I added QED. I don't know who put this in my head, but I had always thought QED was the acronym for Quite Easily Done. And I asked Sean if he knew what QED stood for.

His eyes lit up and he said, "Well, some people say it stands for Quite Enough Done, but actually, it is Latin or maybe Greek for quod erat demonstrandum, which means "that which was to be demonstrated."" My jaw almost dropped :)

Found this on wikipedia:

"The phrase quod erat demonstrandum is a translation into Latin from the Greek ὅπερ ἔδει δεῖξαι (hoper edei deixai; abbreviated as ΟΕΔ). Translating from the Latin into English yields, "that which was to have been demonstrated"; however, translating the Greek phrase ὅπερ ἔδει δεῖξαι produces a slightly different meaning. A better translation from the Greek would read, "precisely what was required to be proved."[2] The phrase was used by many early Greek mathematicians, including Euclid[3] and Archimedes. These mathematicians, in particular Euclid, are credited with founding axiomatic mathematics with its emphasis on establishing truths by logical deduction (rather than experimentation or assertion); their use of this phrase symbolizes this emphasis, as well as marking this important step in the development of mathematical philosophy."

And where did Sean get this ancient nugget of knowledge? No where else but from the wonderful Kjartan Poskitt's Essential Arithmetricks. Gotta love the Murderous Math books.

7 comments:

monlim said...

You're finally back!! And you said your jaw ALMOST dropped?? I would've had to pick mine up from the floor!

Tsu Lin + + said...

I always liked QED but somehow forgot what it meant (not that I knew it correctly like Sean the Braniac III knew it)... He's so brilliant for his age!
And hmm, i've bought 1 of Kjartan Poskitt's books wanted to give it as a present to a friend's son but have since forgotten to pass it on.. so now I'm waiting for SW to "be of age" to have her reading it!

Lilian said...

Haha Mon, I'm really amazed at the kind of things kids retain in their head and then spurt them out out of nowhere.

Tsulin: You know, at one time, a UK online bookshop was having this fantastic Murderous Math deal, can buy the entire series for only about 10 or 15 pounds. I already had them all BUT I should have still bought a new set cos in Sean's hands, the books are now really kiamchye and pages have gone missing.

Tsu Lin + + said...

Which online bookshop is that?

Lilian said...

www.thebookpeople.co.uk

Free delivery with 25pounds purchase. Go crazy! :)

Tsu Lin + + said...

Oh no, and I was hoping after getting a new camera strap, i will not have to BUY ANYTHING ANYMORE! Thanks alot! :P

Lilian said...

Hee hee :)