\[f(t) = a_0 + \sum_{n=1}^{\infty}\big [ a_n\cos (nt) + b_n \sin(nt) \big ]\] \[a_0 = \frac{1}{2L}\int_{-L}^{L} f(t) dt\] \[a_n = \frac{1}{L}\int_{-L}^{L} f(t)\cos \frac{n\pi t}{L} dt\] \[b_n = \frac{1}{L}\int_{-L}^{L} f(t)\sin \frac{n\pi t}{L} dt\]
\[f(t) = a_0 + \sum_{n=1}^{\infty}\big [ a_n\cos (nt) + b_n \sin(nt) \big ]\] \[a_0 = \frac{1}{2L}\int_{-L}^{L} f(t) dt\] \[a_n = \frac{1}{L}\int_{-L}^{L} f(t)\cos \frac{n\pi t}{L} dt\] \[b_n = \frac{1}{L}\int_{-L}^{L} f(t)\sin \frac{n\pi t}{L} dt\]