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[[Problem 1 _Old Kiwi| PS7.1]]
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[[Jets7.1 _Old Kiwi| Solution to 7.1]]
  
8.<math>(\Rightarrow)</math> First we apply Tchebyshev to <math>E_n</math> and find that
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[[Jets7.2 _Old Kiwi| Solution to 7.2]]
  
<math> (n-1)\left|\{x \in X \mid |f(x)| \geq n-1 \}\right| \leq \int_{E_n}|f|</math>
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[[Jets7.3 _Old Kiwi| Solution to 7.3]]
  
or rather
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[[Jets7.4 _Old Kiwi| Solution to 7.4]]
  
<math>(n-1) m(E_n) \leq \int_{E_n}|f|</math>
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[[Jets7.5 _Old Kiwi| Solution to 7.5]]
  
Since we have that <math>m(E_n)</math> is finite we can move it to the other side of the inequality.
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[[Jets7.6 _Old Kiwi| Solution to 7.6]]
  
<math>nm(E_n) \leq \int_{E_n}|f| + m(E_n)</math>
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[[Jets7.7 _Old Kiwi| Solution to 7.7]]
  
Since this is true for all <math>n</math> we take sums on both sides and note that the <math>E_n</math> are disjoint.
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[[Jets7.8 _Old Kiwi| Solution to 7.8]]
 
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<math>\sum_{n=1}^{\infty}nm(E_n) \leq \sum_{n=1}^{\infty}\int_{E_n}|f| + \sum_{n=1}^{\infty}m(E_n)</math>
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or
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<math>\sum_{n=1}^{\infty}nm(E_n)\leq \int_{X}|f| + m(X)</math>
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And we are in a finite measure space so <math>m(X) < \infty</math> and since <math>f \in L^1</math> we have <math>\int_{X}|f| < \infty</math>.
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Thus we have that  <math>\sum_{n=1}^{\infty}nm(E_n) < \infty</math>.
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<math>(\Leftarrow)</math> Since <math>|f|< n</math> in each <math>E_n</math> we have that
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<math>\int_X|f| = \sum_{n=1}^{\infty}\left(\int_{E_n}|f|\right) \leq \sum_{n=1}^{\infty}\left( n m(E_n)\right)< \infty</math>
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In other words, <math> f \in L^1</math>.
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Latest revision as of 17:17, 11 July 2008

Solution to 7.1

Solution to 7.2

Solution to 7.3

Solution to 7.4

Solution to 7.5

Solution to 7.6

Solution to 7.7

Solution to 7.8

Alumni Liaison

BSEE 2004, current Ph.D. student researching signal and image processing.

Landis Huffman