Fourier decomposition and heat equation

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SUMMARY

The discussion focuses on deriving the initial coefficients \( a_k(0) \) in the heat equation \( T(t,x) = \sum a_k(t)b_k(x) \) using Fourier decomposition. The initial temperature distribution \( f(x) \) is defined with boundary conditions \( f(0) = 0 \) and \( f(1) = 0 \). The solution involves expressing \( f(x) \) as \( f(x) = T(0,x) = \sum a_k(0)b_k(x) \), where \( b_k(x) \) are orthonormal functions. The challenge lies in simplifying this equation to isolate \( a_k(0) \) through integration techniques that leverage the orthogonality of the eigenfunctions.

PREREQUISITES
  • Understanding of the heat equation and its boundary conditions.
  • Knowledge of Fourier series and decomposition methods.
  • Familiarity with orthonormal functions and their properties.
  • Basic calculus, particularly integration techniques.
NEXT STEPS
  • Study the derivation of Fourier coefficients in the context of boundary value problems.
  • Learn about the properties of orthonormal functions in Hilbert spaces.
  • Explore integration techniques for computing coefficients in Fourier series.
  • Investigate specific examples of the heat equation with varying initial conditions.
USEFUL FOR

Students and professionals in applied mathematics, particularly those studying partial differential equations, as well as engineers and physicists working with heat transfer problems.

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Homework Statement



In the heat equation, we have $T(t,x)=sum of a_k(t)b_k(x)$.
Now I want to find a formula for computing the initial coefficients $a_k(0)$ given the initial temperature distribution $f(x)$.

Homework Equations


We know that in a heat equation , $f(0)=0$, $f(1)=0$



The Attempt at a Solution


Using Fourier decomposition, we know $f(x)=T(0,x)=a_1(0)b_1(x)+a_2(0)b_2(x)+...+a_k(0)b_k(x)$, and b_k(x) are
orthonormal, but then I don't know how to simplify this equation to get a function of $a_k(0)$
 
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conisider inetgrating something like f(x)sin(kx) taking into account the orthogonal nature of the eigenfunctions
 

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