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Topic: Research on "Twice as big"
Replies: 19   Last Post: Feb 27, 2011 1:15 PM

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kirby urner

Posts: 1,637
Registered: 11/29/05
Re: Research on "Twice as big"
Posted: Jan 31, 2011 6:12 PM
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On Mon, Jan 31, 2011 at 12:20 PM, Jonathan Crabtree <
sendtojonathan@yahoo.com.au> wrote:

> Hi Dave
>
> The question why people can't draw twice as big or twice as much is
> interesting to me.
>
> Whether or not the question is unclear may depend on innate thinking
> styles. That's my hypothesis.
>
> Mathematicians have the right to defend a square twice as big having four
> times the area and claim the question is wrong.
>
>

You might be interested in this thread on mathfuture, where Ed Cherlin tells
the story of Apollo's altar:

> As I said before, we state: the ratio of circumference of a circle to its
> diameter is pi. Like it is the most natural thing in the world. I think

it
> is EXTREMELY strange. and I will bet that the Greeks (or whoever
discovered
> pi) thought God must be having some fun.

Not so much. However, the cube root of 2 is known to be a prank of the
Greek gods. Apollo demanded through his oracle at Delphi that the
Greeks double the size of his cubical altar. First they doubled the
side, which made it eight times larger, then they proved that 2^(1/3)
cannot be constructed with ruler and compass, and sacrificed 100 bulls
instead. Apollo is on record as being pleased with their solution, or
so the Greeks wrote down in their histories.

Euclidean constructions allow addition, subtraction, multiplication,
division, and square roots, just like a five-function calculator. It
is not very difficult to prove that cube roots don't qualify, in
somewhat the same way that one proves that square root of 2 is
irrational.

http://groups.google.com/group/mathfuture/msg/131e00df54934d1b?hl=en
<http://groups.google.com/group/mathfuture/msg/131e00df54934d1b?hl=en>

I'm not familiar with the proof Ed is talking about. You or Dave might
know.

Kirby



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