The nth partial sum of a Fourier series is defined as: A_{0}+A_{1} \cos \omega_{1} t+B_{1} \sin \omega_{1} t+\ldots+A_{n} \cos \omega_{n} t+B_{n} \sin \omega_{n} t y(t)=\sum_{n=1}^{\infty} \frac{3 n}{2} \sin n+\frac{5 n}{3}

\cos n t For the third partial sum of the Fourier series given by a) What is the fundamental frequency and the associated period? b) Express this partial sum as cosine terms only.