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Fourier series for complex numbers


Convergence in the mean of Fourier seriesDeriving fourier series using complex numbers - introductionFourier Coefficients of a Sequence of FunctionsFourier Series of Real-valued FunctionsComputing the Fourier series of $lvert xrvert$Cauchy Product of Fourier Series with itselfBasic Properties Of Fourier Series. 2.To show non-existence of Riemann integrable function whose positive Fourier coefficients are $1/n$ and non-positive Fourier coefficients are zeroDetermining $N$ when calculating a fourier seriesWrong value of sum using fourier series













-1












$begingroup$


A certain riemann-integrable function $f:[-pi,pi] rightarrow mathbbC $ and a complex number sequence $c_k$ obey



$ |lvert f(t) -sum_k=-n^n c_ne^ikt|rvert_2 rightarrow 0$ as $n rightarrow infty$



Prove:



For any $ g:[-pi,pi] rightarrow mathbbC$ with $ginmathbbR[-pi,pi]$



$frac12piint_-pi^pi f(t)overlineg(t)=
sum_k=-infty^infty c_koverlinehatg(k)$
, where $hatg(k)= int_-pi^pi g(t)e^-iktdt$. Given this, prove $c_k =hatf(k)$ and $sum_k lvert c_k rvert^2 < infty$



I am not sure how to approach this problem. I learnt Fourier analysis for real numbers but the complex numbers are confusing me. Thank you










share|cite|improve this question











$endgroup$
















    -1












    $begingroup$


    A certain riemann-integrable function $f:[-pi,pi] rightarrow mathbbC $ and a complex number sequence $c_k$ obey



    $ |lvert f(t) -sum_k=-n^n c_ne^ikt|rvert_2 rightarrow 0$ as $n rightarrow infty$



    Prove:



    For any $ g:[-pi,pi] rightarrow mathbbC$ with $ginmathbbR[-pi,pi]$



    $frac12piint_-pi^pi f(t)overlineg(t)=
    sum_k=-infty^infty c_koverlinehatg(k)$
    , where $hatg(k)= int_-pi^pi g(t)e^-iktdt$. Given this, prove $c_k =hatf(k)$ and $sum_k lvert c_k rvert^2 < infty$



    I am not sure how to approach this problem. I learnt Fourier analysis for real numbers but the complex numbers are confusing me. Thank you










    share|cite|improve this question











    $endgroup$














      -1












      -1








      -1





      $begingroup$


      A certain riemann-integrable function $f:[-pi,pi] rightarrow mathbbC $ and a complex number sequence $c_k$ obey



      $ |lvert f(t) -sum_k=-n^n c_ne^ikt|rvert_2 rightarrow 0$ as $n rightarrow infty$



      Prove:



      For any $ g:[-pi,pi] rightarrow mathbbC$ with $ginmathbbR[-pi,pi]$



      $frac12piint_-pi^pi f(t)overlineg(t)=
      sum_k=-infty^infty c_koverlinehatg(k)$
      , where $hatg(k)= int_-pi^pi g(t)e^-iktdt$. Given this, prove $c_k =hatf(k)$ and $sum_k lvert c_k rvert^2 < infty$



      I am not sure how to approach this problem. I learnt Fourier analysis for real numbers but the complex numbers are confusing me. Thank you










      share|cite|improve this question











      $endgroup$




      A certain riemann-integrable function $f:[-pi,pi] rightarrow mathbbC $ and a complex number sequence $c_k$ obey



      $ |lvert f(t) -sum_k=-n^n c_ne^ikt|rvert_2 rightarrow 0$ as $n rightarrow infty$



      Prove:



      For any $ g:[-pi,pi] rightarrow mathbbC$ with $ginmathbbR[-pi,pi]$



      $frac12piint_-pi^pi f(t)overlineg(t)=
      sum_k=-infty^infty c_koverlinehatg(k)$
      , where $hatg(k)= int_-pi^pi g(t)e^-iktdt$. Given this, prove $c_k =hatf(k)$ and $sum_k lvert c_k rvert^2 < infty$



      I am not sure how to approach this problem. I learnt Fourier analysis for real numbers but the complex numbers are confusing me. Thank you







      fourier-series






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Mar 13 at 18:11









      uniquesolution

      9,2911823




      9,2911823










      asked Mar 13 at 17:44









      Kaan YolseverKaan Yolsever

      1309




      1309




















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