Lecture 17

Ch 4, first half of sec 2

State the Siefert-Van Kampen Theorem 2.1, and its generalization Theorem 2.2. Prove Lemma 2.3. This theorem has a rather abstract statement - what, intuitively, is it saying? (Consult Hatcher for a more palitable formulation, Theorem 1.20 of Chapter 1)