- #1
snesnerd
- 26
- 0
If you take the Fourier series of a function $f(x)$ where $0 < x < \pi$, then would $a_{0}$, $a_{n}$, and $b_{n}$ be defined as,
$a_{0} = \displaystyle\frac{1}{\pi}\int_{0}^{\pi}f(x)dx$
$a_{n} = \displaystyle\frac{2}{\pi}\int_{0}^{\pi}f(x)\cos(nx)dx$
$b_{n} = \displaystyle\frac{2}{\pi}\int_{0}^{\pi}f(x)\sin(nx)dx$
assuming that I am using the definition of a Fourier series in the following way:
$f(x) = \displaystyle\frac{a_{0}}{2} + \sum_{k=1}^{\infty}a_{n}\cos\left(\frac{n\pi x}{L}\right) + b_{n}\sin\left(\frac{n\pi x}{L}\right)$
I only ask because I found this article:
http://people.uncw.edu/hermanr/mat463/ODEBook/Book/Fourier.pdf
On page 163 he defines the Fourier series from $[0,L]$ but in his definition, he has
$\cos\left(\frac{2n\pi x}{L}\right)$ and $\sin\left(\frac{2n\pi x}{L}\right)$ in his formulation. Is the way I set it up correct or his way? I have seen it both ways. I have also seen $a_{0}$ defined with the constant $\displaystyle\frac{2}{\pi}$ in front of the integral at times too so I am unsure if mine is correct or I need to add the two.