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[[Jets7.1 _OldKiwi| Solution to 7.1]]
 
[[Jets7.1 _OldKiwi| Solution to 7.1]]
  
[[Jets7.5 _OldKiwi| Solution to 7.5]]
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[[Jets7.2 _OldKiwi| Solution to 7.2]]
  
8.<math>(\Rightarrow)</math> First we apply Tchebyshev to <math>E_n</math> and find that
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[[Jets7.3 _OldKiwi| Solution to 7.3]]
  
<math> (n-1)\left|\{x \in X \mid |f(x)| \geq n-1 \}\right| \leq \int_{E_n}|f|</math>
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[[Jets7.4 _OldKiwi| Solution to 7.4]]
  
or rather
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[[Jets7.5 _OldKiwi| Solution to 7.5]]
 
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<math>(n-1) m(E_n) \leq \int_{E_n}|f|</math>
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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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<math>nm(E_n) \leq \int_{E_n}|f| + m(E_n)</math>
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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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<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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[[Jets7.6 _OldKiwi| Solution to 7.6]]
  
<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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[[Jets7.7 _OldKiwi| Solution to 7.7]]
  
In other words, <math> f \in L^1</math>.
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[[Jets7.8 _OldKiwi| Solution to 7.8]]

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

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