\[
\begin{aligned}
&f(t) = a_0 + \sum_{n=1}^{\infty}\left[ a_n \cos(\omega nt) + b_n \sin(\omega n t)\right]\\
\\
&a_0 = \frac{1}{T} \int_{0}^{T} f(t)dt\\
\\
&a_n = \frac{2}{T}\int_{0}^{T}f(t)\cos(2 \pi n t)\\
\\
&b_n = \frac{2}{T}\int_{0}^{T}f(t)\sin(2 \pi n t)\\
\\
&\omega = \frac{2\pi}{T}, \text{ called the fundamental frequency}\\
\\
& \text{Where } T \text{ is the period of our function. The value such that } f(t) = f(t + T) \ \forall t \\
\end{aligned}
\]