Corollary 2

Tag 023G, permanent. Cite it as [Bourbaki, Tag 023G].

Topologie algébrique, chapter IV, § 5. Théorème de van Kampen

If the group $\pi_1(X, a)$ is trivial, the set A = $B\cap C$ is arcwise connected; if it is commutative, the set A has at most two arcwise connected components.

In fact, if S is a set, the free group F(S) is trivial only if S is empty and is commutative only if Card $S\leqslant 1$ .

Bourbaki sets the proof directly after the statement, and the corpus does not separate them, so what is above is the statement and its proof together.

Cited by

Nothing.

Cites

Nothing.