3 ms·
I have been fascinated by these integrals for a long time and am happy to see them getting more attention. 3Blue1Brown recently made a video on the topic: http
by deepspace 4y ago
I have been fascinated by these integrals for a long time and am happy to see them getting more attention. 3Blue1Brown recently made a video on the topic: https://www.youtube.com/watch?v=851U557j6HE https://www.youtube.com/watch?v=851U557j6HE
What strikes me is the reminder that it is never possible to "prove" something by pointing out that it is true for all known cases. (See also Black Swan events). In Greg Egan's example, if you stopped testing at 10^43 iterations, you would be very tempted to conclude that the identity holds for all n, for example.
- _nalply 4y agoTo prove something for all n you need to do mathematical induction: First prove that something is true for some n, usually n = 1. Then prove that if it's true for n it's for n + 1, too. Boom. It's true for all n. But the second step is sometimes very hard or even perhaps impossible.
- Chinjut 4y agoInduction is one way to prove something for all n but hardly the only way.
- galaxyLogic 4y ago> Then prove that if it's true for n it's for n + 1, too. Or you might be able to prove that it is true for n + 2 but not be able to prove it is true for n + 1. Right?
- c7b 4y ago> What strikes me is the reminder that it is never possible to "prove" something by pointing out that it is true for all known cases. Not exactly true. If you can prove that the cases you checked amount to all the cases in the theorem statement, you're done. The Four-color theorem is a well-known example that was originally proved in this way (accompanied by a controversy about whether that's a 'real' proof, which is arguably pretty much settled at this point). Induction would arguably be another way (that only requires checking a single case).