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MCS,PHD
Argosy University/ Phoniex University/
Nov-2005 - Oct-2011
Professor
Phoniex University
Oct-2001 - Nov-2016
Is the function described in Example 5.4 uniformly continuous on X?
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Example 5.4
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Let (X1, d1) and (X2, d2) be metric spaces, let f: X1 → X2, and let c ∈ X1. Then the following three conditions are equivalent:
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(a) f is continuous at c.
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(b) If (xn) is any sequence in X1 such that (xn) converges to c, then (f(xn)) converges to f(c) in X2.
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(c) For every neighborhood V of f(c) in X2, there exists a neighborhood U of c in X1 such that f(U) ⊆ V.
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(a) ⇒ (b) Suppose f is continuous at c and let (xn) be a sequence in X1 such that xn → c. Given ε > 0, since f is continuous at c there exists
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(c) ⇒ (a) Given any ε > 0, let V = N(f(c); ε). By our hypothesis in (c), there exists a neighborhood U = N(c; δ ) such that f (U ) ⊆ V. But then whenever d1(x, c) < δ="" we="" have="" x="">∈ U, so f (x) ∈ V and d2( f (x), f (c)) < ε.="" thus="" f="" is="" continuous="" at="">
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