Chapter 17, Problem 15P

Express the Fourier series

$f\left(t\right)=10+{\displaystyle \underset{n=1}{\overset{\infty }{\sum }}\frac{4}{n^2+1}\cos 10nt+\frac{1}{n^3}\sin 10nt}$

1. (a) in a cosine and angle form,
2. (b) in a sine and angel form.