Proving Rudin Theorem 7.17: Real Analysis

In summary, the conversation is discussing the proof of a remark made by Rudin in theorem 7.17 of his book Mathematical Analysis. The goal is to prove that if a sequence of functions, {fn}, is differentiable on [a,b] and converges for some x0 in [a,b], and if the derivative of {fn}, f'n, is continuous for every n and converges uniformly to a function f, then {fn} also converges uniformly to f and f'(x) = lim(n goes to inf) f'n(x). Rudin's hint for the proof is to use theorem 7.16 and the fundamental theorem of calculus.
  • #1
algekkk
6
0
i am asked to prove the remark Rudin made in theorem 7.17 in his Mathematical Analysis.

Suppose {fn} is a sequence of functions, differentiable on [a,b] such that {fn(x0)} converges for some x0 in [a,b]. Assume f'n (derivative of fn) is continuous for every n. Show if {f'n} converges uniformly, then {fn} converges uniformly to some function f and f'(x)=lim(n goes to inf) f'n(x). (x in [a,b])

Rudin's hint is to use theorem 7.16 and fundamental theorem of calculus.


Thanks for any help.
 
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  • #2
Please follow the outline for posts given in the sticky -- in particular, you should (section 2) give the statement of theorem 7.16, since not everyone here has a copy of Rudin, and (section 3) tell us what you've done so far.
 

1. What is Rudin Theorem 7.17 in Real Analysis?

Rudin Theorem 7.17, also known as the Lebesgue Differentiation Theorem, states that for a function f in L1, the Lebesgue integral of f over any interval [a,b] can be approximated by the average value of f over that interval. In other words, the Lebesgue integral of f is equal to the average value of f over [a,b].

2. Why is Rudin Theorem 7.17 important in Real Analysis?

Rudin Theorem 7.17 is important because it provides a powerful tool for evaluating integrals in a more flexible way than the Riemann integral. It also allows for the integration of more general types of functions, such as discontinuous or unbounded functions, which cannot be integrated using the Riemann integral.

3. How is Rudin Theorem 7.17 proven?

The proof of Rudin Theorem 7.17 involves using the Lebesgue measure and integral, and the concept of convergence in measure. It also relies on the construction of the Lebesgue integral as a limit of Riemann sums. The details of the proof can be found in Rudin's book "Principles of Mathematical Analysis".

4. Can Rudin Theorem 7.17 be extended to higher dimensions?

Yes, Rudin Theorem 7.17 can be extended to higher dimensions. In fact, the Lebesgue Differentiation Theorem holds for functions defined on any measure space, not just the real line. This allows for the integration of functions in multiple dimensions, such as in multivariable calculus.

5. What are the applications of Rudin Theorem 7.17 in Real Analysis?

Rudin Theorem 7.17 has many applications in real analysis, including the evaluation of integrals involving discontinuous or unbounded functions, the construction of the Lebesgue integral, and the development of the Riesz representation theorem. It also has applications in areas such as probability theory, harmonic analysis, and differential equations.

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