Notre Dame Journal of Formal Logic

Weak König's Lemma Implies Brouwer's Fan Theorem: A Direct Proof

Hajime Ishihara


Classically, weak König's lemma and Brouwer's fan theorem for detachable bars are equivalent. We give a direct constructive proof that the former implies the latter.

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Notre Dame J. Formal Logic, Volume 47, Number 2 (2006), 249-252.

First available in Project Euclid: 25 July 2006

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Zentralblatt MATH identifier

Primary: 03F65: Other constructive mathematics [See also 03D45]
Secondary: 03B30: Foundations of classical theories (including reverse mathematics) [See also 03F35]

weak Koenig's lemma Brouwer's fan theorem constructive mathematics


Ishihara, Hajime. Weak König's Lemma Implies Brouwer's Fan Theorem: A Direct Proof. Notre Dame J. Formal Logic 47 (2006), no. 2, 249--252. doi:10.1305/ndjfl/1153858649.

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