Show it is a Banach-Space

WieZo

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Apr 10, 2009
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Hello everyone, I'm completly new to this topic, so I don't have any clue on this

Let \(\displaystyle A \subset \mathbb{R}^n\) and \(\displaystyle f \in C^l(\overline{A})\)

Show that \(\displaystyle \ ( C^l(\overline{A}) , \ \| f\|_{l,\infty,A} )\) is a banach space, where

\(\displaystyle \| f\|_{l,\infty,A} := \max_{|d| \le l } \sup_{x \in A} | \partial^d f(x) |\)

All I know is that I need to show: \(\displaystyle ( C^l(\overline{A}) , \ \| f\|_{l,\infty,A} )\) is complete, e.g. every cauchy sequence convergences

If (f_n) is a cauchy sequence in C^l, why does a f in C^l exist with f_n converges to f?

I don't get it, so can someone help me out of this problem, pls? This would be great

Thank you
 
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