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Alex Kim
Alex Kim
May 9, 2026

Can ChatGPT prove that sqrt(2) is irrational?

I asked ChatGPT to prove 2\sqrt{2}2​ is irrational and it gave a perfect proof:

Assume 2=pq\sqrt{2} = \frac{p}{q}2​=qp​ in lowest terms. Then 2=p2q22 = \frac{p^2}{q^2}2=q2p2​ so p2=2q2p^2 = 2q^2p2=2q2. So p2p^2p2 is even, hence ppp is even. Write p=2rp = 2rp=2r. Then 4r2=2q24r^2 = 2q^24r2=2q2 so q2=2r2q^2 = 2r^2q2=2r2. So q2q^2q2 is even, hence qqq is even. Contradiction since ppp and qqq were in lowest terms.

But heres the thing: this is just Euclids proof from 300 BC. The AI didnt "discover" anything, it just reproduced what it was trained on.

My question: Is AI capable of generating NOVEL mathematical proofs? Or is it just a sophisticated search engine that regurgitates existing mathematics?

What would it take for an AI to genuinely extend mathematical knowledge?

1 answers1.4k views

1 Answer

2
Emily Park
Emily Park
May 23, 2026
Accepted
ChatGPT can present a valid proof that $\sqrt2$ is irrational, but that does not mean it discovered the proof from scratch. The usual proof is classical: Assume: $$\sqrt2=\frac{p}{q}$$ in lowest terms. Then: $$p^2=2q^2.$$ So $p$ is even. Write $p=2k$. Then: $$q^2=2k^2,$$ so $q$ is even too. That contradicts the assumption that $p/q$ was in lowest terms. If an AI gives exactly this argument and every logical step is correct, then the proof is valid as a proof. But the source of the proof is likely reproduction and recombination of known mathematics, not original discovery. The important skill is verification: check assumptions, check each implication, and make sure the contradiction really follows.
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