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I am reading algebraic topology, chapter 2 by Hatcher.

In page 136, he proves that

$$\deg f = \sum_i \deg f\mid x_i.$$ I understood something, but I am not convinced. Can someone explain the proof?

Thanks in advance.

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What exactly do you not understand about the proof? Can you say anything specific? There is a big diagram in there, perhaps you can say something about the diagram that you don't understand? –  user38268 Nov 28 '12 at 22:40
Also please improve your accept rate from 20%. –  user38268 Nov 28 '12 at 22:40
Can you tell us the exact definitions? –  Berci Nov 28 '12 at 23:30

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