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Forum URL: http://www.cut-the-knot.org/cgi-bin/dcforum/forumctk.cgi
Forum Name: Middle school
Topic ID: 35
#0, Just a Curious Monkey Question...?
Posted by MathWiz on Jan-30-01 at 04:35 PM
Why is the pythagorean Therom only true for right triangles?

#1, RE: Just a Curious Monkey Question...?
Posted by alexb on Jan-30-01 at 04:42 PM
In response to message #0
Assume a, b, c are the sides of a triangle which is not right, but for which nonetheless a2 + b2 = c2.

Position the sides a and b as to make a right angle. Let d be the distance between their endpoints. By the Pythagorean theorem,
a2 + b2 = d2. Which implies

c2 = d2.

From where, c = ±d. However, both c and d are positive from the context. Therefore, c = d in the first place. Therefore, the original triangle was in fact right.


#2, RE: Just a Curious Monkey Question...?
Posted by MathWiz on Feb-06-01 at 04:42 PM
In response to message #1
What's the connection with the Pythagorean Therom area of squares and Pythagorean Triples?

#3, RE: Just a Curious Monkey Question...?
Posted by alexb on Feb-06-01 at 04:44 PM
In response to message #2
> What's the connection with the
> Pythagorean Therom area of squares
> and Pythagorean Triples?

I do not understand your question.


#4, RE: Just a Curious Monkey Question...?
Posted by MathWiz (Guest) on Feb-07-01 at 09:22 AM
In response to message #3
I want to know how they are all interalted, if it's not too much to ask. What I want to know is how the area of squares applies tothe Pythagorean Therom, and Pythagorean Triples. How they all fit together.

#5, RE: Just a Curious Monkey Question...?
Posted by alexb on Feb-07-01 at 11:32 AM
In response to message #4
The Pythagorean theorem asserts that the sum of areas of the squares constructed on the legs of a right triangle equals the area of the square built on its hypotenuse.

Between us, I am uncomfortable answering your questions. This is because I get a feeling that my effort - however small - of typing the answers goes nowhere. You have never followed up on your first question, although I did expect you to.


#6, RE: Just a Curious Monkey Question...?
Posted by MathWiz on Feb-07-01 at 04:43 PM
In response to message #5
Well, I think that your input that you could give me on to this question would be much greater then any ideas that I could ever come up with, becase your page on proofs for the Pythagorean Therom is truely amazing. Yes, I still am wondering why the Pythagorean Therom is only true for right triangles, becauase I did not understand the frst sentece of your origional response to that question. Any input tht you have would be greatly appreciated. Thank you :)

#7, RE: Just a Curious Monkey Question...?
Posted by alexb on Feb-07-01 at 04:51 PM
In response to message #6
>Well, I think that your input
>that you could give me
>on to this question would
>be much greater then any
>ideas that I could
>ever come up with,

Not so, as the last sentence in your message shows very clearly. I can waste plenty of time unless you make some effort at trying to understand both your question and my answer.

> becase
>your page on proofs for
>the Pythagorean Therom is truely
>amazing.

Thank you. But this is irrelevant as you apparently did not get the point.

> Yes, I still
>am wondering why the Pythagorean
>Therom is only true for
>right triangles, becauase I did
>not understand the frst sentece
>of your origional response to
>that question.

The first sentence reads:

Assume a, b, c are the sides of a triangle which is not right, but for which nonetheless a2 + b2 = c2.

Which means, "Assume there is a triangle which is not right but for which the Pythagorean theorem holds nonetheless."

What follows afterwards is a demonstration that that assumption leads to a contradiction.

>Any input
>tht you have would be
>greatly appreciated. Thank you
>:)