Too much brute force can kill you!

Geometry Level 5

$\large{\xi=\frac{\sin0^\circ+\sin\frac{\phi}{n}+\sin\frac{2\phi}{n}+\cdots+\sin\frac{(n-1)\phi}{n}+\sin\phi}{\cos0^\circ+\cos\frac{\phi}{n}+\cos\frac{2\phi}{n}+\cdots+\cos\frac{(n-1)\phi}{n}+\cos\phi}}$

The above ratio can be expressed in a simplified form. You may want to find that form first.

If $$n=71$$ and $$\phi=71^\circ$$, then what is the value of $$\xi$$?