Hurewicz theorem

The proof of Hurewicz theorem is outside the scope of this book. Instead, we formulate some useful corollaries for future reference. For both statements, assume that X is a CW complex, and that A and B are CW subcomplexes, such that X = A U B. 

Proof. By Hurewicz Theorem 6.28, all homotopy groups are trivial as well hence we may use Corollary 6.32. ... 

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