Proof. Starting with the continuous map in Lemma 3.19, we can determine the pre-image of : let be a point and be its unique pre-image under , where and . By Lemma 3, if we fix a non-zero element , the point lies in if and only if
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This condition is equivalent to
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Hence there exists a continuous surjective map
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If we remove and from the domain and image, the restricted map is indeed a homeomorphism.
∎