# Solving an ODE using Galerkin's method

1. Oct 16, 2008

### Breuno

1. The problem statement, all variables and given/known data
Given the ODE $$\frac{df}{dt}=f$$ and the boundary condition $$f(0)=1$$

One approximate solution is $$f_{a}=1+\sum ^{3}_{k=1} a_{k}t^k$$ where $$0\leq t\leq1$$

Using the Galerkin's method find the coeficents $$a_{k}$$
2. Relevant equations

3. The attempt at a solution
I don't think I've understood how to use the method really. So if someone could explain it briefly. Another thing that is mentioned in the book is that the basis funktions are not orthogonal on this interval. So that can not be imposed

Thanks
/Simon

2. Oct 16, 2008

### nasu

You can take the derivative of the general (approximate) solution and plug in the equation.
Then equate the terms with the same power of t and you'll get 3 simple equations that will give you the three coefficients a1, a2, a3.