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Homework Help: Heat Flow Problem

  1. May 9, 2009 #1
    1. The problem statement, all variables and given/known data

    Find a formal solution to the given initial boundary value problem.

    du/dt=5(d^2u/dx^2) 0<x<1 t>0
    u(0,t)=u(1,t)=0 t>0
    u(x,0)=(1-x)(x^2) 0<x<1

    2. Relevant equations

    1) u(x,t) = a0/2 + sum[an*e^(-b(n pi/L)^2*t) * cos(n pi x/L)

    2) Fourier series equation

    3. The attempt at a solution

    (1-x)(x^2) = a0/2 + sum(an * cos(n pi x) with cn = an

    I calculate a0=1/6

    an = 2* integral[(1-x)(x^2)(cos n pi x)dx] from 0 to 1

    I'm wondering if this is write so far? And if so, how do I proceed from here? Do I just plug everything back into the general u(x,t) equation?

  2. jcsd
  3. May 9, 2009 #2
    You might not want to use the cosine series. Since one of your BC's is u(0,t) = 0. You will never satisfy that condition when cos(0) = 1. Try using the sine series instead.
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