— 398 — 
cos 
r-faA 
2(p — l)m 2 pm 
cos— — n — 0cos — — n 
n n 
0 2 — 2^cos — 77-4-1 
ii 
e 2 - 20COS !t -I- 1 
n 
-K... 
(n — 2)(p — 1) (n— 2)p 
COS- — 7 — 0COS — 77 
Il II 
.••••“» — — 5 
9 2 ~ 20cos(^— - — ^77 -I- 1 
ed in questa formula cangiando p nella n pari, avremo il valore della frazione 
Qn-l 
1 - 0 * ’ 
Moltiplicando poi per dQ la differenza delle due frazioni così trovate, otterremo 
Q P -l_ Qn - 1 
2 
n 
1 — 0 * 
2 p 
de. 
i-(-i ) 7 
2(0 h- 1) 
(\ - cos ^ 77)0 
V ?7 ' 
2 (p - 1) 2 
COS — £ 7 T — COS —77 
n n 
(l — COS — 77 ^0 
s2 
0 2 — 20COS 77— t— 1 
11 
4 (p — 1) 4 
COS 77 — COS — 77 
77 77 
4 -.... 
0 2 — 20COS — 77 -+- 1 
77 
(l — COS 77 ^0 -+* COS 
2(p — l)m 2/77 
— — 77 — COS 77 
77 77 
0 2 — 20COS -77-4-1 
77 
/ ( 77 — 2 p \ ( 77 — 2 (p — 1) 
( 1 COS - 77 )0-t— COS - — -77 
\ 77 > 77 
e 2 — 29coslÌ^ n -t-t 
77 2 ~S 
COS ^ 
77 
77 
d0 
