The value of a Fourier series at a jump point (discontinuity)

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SUMMARY

The discussion centers on the evaluation of a Fourier series at a discontinuity, specifically at the point x=e. The participant highlights that the limit of the function f(x) approaches -infinity as x approaches e, while the function value at that point is f(e)=1. This situation indicates that the function does not meet the Dirichlet conditions, which are essential for the convergence of Fourier series. Consequently, the standard convergence theorem cannot be applied in this case.

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Amaelle
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Homework Statement
calculate the value of the fourier serie at x=e for the e periodic function (0,e]
f(x)=log(x)
Relevant Equations
Fourier serie
Greetings
according to the function we can see that there is a jump at x=e and I know that the value of the function at x=e should be the average between the value of f(x) at this points
my problem is the following
the limit of f(x) at x=e is -infinity and f(e)=1
how can we deal with such situations?

thank you!
 
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Since ##f(0^+) = -\infty##, your function doesn't satisfy the Dirichlet conditions, so the usual theorem about convergence doesn't apply.
 
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LCKurtz said:
Since ##f(0^+) = -\infty##, your function doesn't satisfy the Dirichlet conditions, so the usual theorem about convergence doesn't apply.
thanks a million!
 

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