(C^{0,\alpha}(\bar{\Omega}), \|\cdot\|_{C^{0,\alpha}(\bar{\Omega})})
is a Banach space
Let f_n be a cauchy sequence in C^{0,\alpha}(\bar{\Omega}). Therefore, for every
\epsilon > 0 there exits M such that for all n,m > M, we have
\|f_n-f_m\|_{C^{0,\alpha}(\bar{\Omega})} < \epsilon. This gives that
[f_n-f_m]_{C^{0,\alpha}(\bar{\Omega})} < \epsilon and \|f_n -f_m\|_{C^0(\bar{\Omega})} < \epsilon. From the latter we get that
f_n converges (in the sup norm) to a bounded continuous function f (on \bar{\Omega}). From the former we get that [f_n-f]_{C^{0,\alpha}(\bar{\Omega})} < \epsilon by letting m \to \infty. Therefore \|f_n-f\|_{C^{0,\alpha}(\bar{\Omega})}
\to 0 as n \to \infty. It remains to show that f \in {C^{0,\alpha}(\bar{\Omega})}
but this follows easily by
[f]_{C^{0,\alpha}(\bar{\Omega})} = [f-f_n+f_n]_{C^{0,\alpha}(\bar{\Omega})} \leq [f-f_n]_{C^{0,\alpha}(\bar{\Omega})} + [f_n]_{C^{0,\alpha}(\bar{\Omega})} < \infty
Note that this result does not depend on \alpha.
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