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Topic: Distance Between Lines in R^3 (fwd)
Replies: 15   Last Post: Sep 13, 2013 1:25 PM

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fom

Posts: 1,968
Registered: 12/4/12
Re: Distance Between Lines in R^3 (fwd)
Posted: Jul 28, 2013 9:38 PM
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On 7/28/2013 8:26 PM, Ken Pledger wrote:
> In article <kt4635$fis$1@news.albasani.net>,
> Thomas Nordhaus <thnord2002@yahoo.de> wrote:
>

>> Am 28.07.2013 23:01, schrieb Ken Pledger:
>>> ....
>>> That's all. It's a traditional method in old text-books which aren't
>>> read much any more, and it doesn't need any calculus.

>>
>> I think implicitly it does....

>
>
> It needs the fact that the shortest path from a point to a line is
> along the perpendicular. My geometry students prove that as a little
> exercise using Euclid I.16 and 19 - definitely no calculus.
>


Have to love those old textbooks.

When I meet people having difficulties,
I often advise them to seek some old
texts from used bookstores. They often
have better expositions.

When I read your post, I thought of
a dusty old book on analytical geometry
by W.K.Morrill.

No calculus needed. Just the definition of
angle in terms of inner product.







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