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Pythagorean Theorem Demonstrated with Fluids. (Original Post) soothsayer Mar 2021 OP
1+ keithbvadu2 Mar 2021 #1
Brilliant in its simplicity Clash City Rocker Mar 2021 #2
Well, it works with that *particular* example ... does that necessarily mean it works with others ? eppur_se_muova Mar 2021 #3
a2+b2 equals c2 intrepidity Mar 2021 #4
Literally, for that particular case, and no other, except by building other demonstrations. eppur_se_muova Mar 2021 #5
Pythagorean applies to right triangle only intrepidity Mar 2021 #6
There are an infinite number of right angled triangles muriel_volestrangler Mar 2021 #7
Yes, it does intrepidity Mar 2021 #8
It shows it for that specific right-angled triangle, not for all of them muriel_volestrangler Mar 2021 #9
Which one does it not apply to? nt intrepidity Mar 2021 #10
It doesn't *show* it for any other. muriel_volestrangler Mar 2021 #11
Are you disputing the Pythagorean Theorem, in general? intrepidity Mar 2021 #12
No, I'm not disputing the theorem; you are missing the difference between one example muriel_volestrangler Mar 2021 #13
Yes, I truly am missing your point nt intrepidity Mar 2021 #14
The point is proving a specific case doesn't prove the generality. Dr. Strange Mar 2021 #15

eppur_se_muova

(36,262 posts)
3. Well, it works with that *particular* example ... does that necessarily mean it works with others ?
Mon Mar 1, 2021, 02:24 PM
Mar 2021

That's the problem with physical examples -- they're specific cases. Actual proofs are general.

I could set up one which shows the fluid in a circle filling up a square, but that would just be the result of very careful measurement for that case. Couldn't give a general rule, and neither can anyone else.

eppur_se_muova

(36,262 posts)
5. Literally, for that particular case, and no other, except by building other demonstrations.
Mon Mar 1, 2021, 02:51 PM
Mar 2021

That is the difference between a demonstration and a proof. The OP says demonstration, which is literally correct. It is not a proof -- literally or otherwise, and the OP doesn't claim it is. Just pointing out the dangers of using such demonstrations to educate.

muriel_volestrangler

(101,312 posts)
7. There are an infinite number of right angled triangles
Tue Mar 2, 2021, 06:23 PM
Mar 2021

Just to take the ones with integer sides: 8,15,17; 3,4,5; 5,12,13; 7,24,25; 9,40,41 ...

Their sides are all in different ratios. A demonstration with one of them doesn't prove it for all of them.

intrepidity

(7,295 posts)
8. Yes, it does
Tue Mar 2, 2021, 08:17 PM
Mar 2021

The liquid measures volume. Assume the depth/height of all figures is 1 (H=1).

Now their volumes (LxWxH) are

a2+b2=c2

Unless I'm really missing something and need to relearn geometry...

muriel_volestrangler

(101,312 posts)
9. It shows it for that specific right-angled triangle, not for all of them
Tue Mar 2, 2021, 08:53 PM
Mar 2021

so it's not a general proof of Pythagoras' Theorem, only a demonstration for specific values of a, b, and c.

muriel_volestrangler

(101,312 posts)
11. It doesn't *show* it for any other.
Wed Mar 3, 2021, 06:46 AM
Mar 2021

It doesn't tell you whether it applies to any other.

If I found that the diagonal of a rectangle was equal to the sum of the 2 shorter sides, that would not prove it as a general property of rectangles.

intrepidity

(7,295 posts)
12. Are you disputing the Pythagorean Theorem, in general?
Wed Mar 3, 2021, 01:47 PM
Mar 2021

Are you also a flat earther??? I'm being serious, this is mind-blowing.

I thought you were disputing the demonstration using liquid, but it seems not.

Wtaf is going on?

Do you agree that, for right triangles: a(squared) + b(squared) = c(squared)?

Is there a semantic nuance I'm missing??

muriel_volestrangler

(101,312 posts)
13. No, I'm not disputing the theorem; you are missing the difference between one example
Wed Mar 3, 2021, 02:06 PM
Mar 2021

and proving the theorem in general. I don't think that's "semantic nuance"; I think it's the idea of "proof of a general theorem". A proof needs to apply to all cases, not just one.

Dr. Strange

(25,921 posts)
15. The point is proving a specific case doesn't prove the generality.
Thu Mar 4, 2021, 08:17 PM
Mar 2021

If I claim that every prime can be written as a sum of two squares of integers, and then "prove" it by saying: 13 = 2^2 + 3^2
does that really work?

No, it just shows that 13 is the sum of two squares. But if you try 7, you get an example that doesn't work.

The demonstration above shows that a particular right triangle satisfies the equation in Pythagoras' Theorem, but the Theorem claims that the result will hold for ANY right triangle.

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