18 SUR LE DEVELOPPEMENT EN SERIES 



4 A la place <le la formule (/"'). 



En changeant les puissances en cosinus des arcs multiples, on obtient : 



(IV). 



/ '" + ' [5 _ i \ 



9 \4 2 X J _ j [2it+l,] [2li 



p + 4-3 



[2lH-5,l][2it-f.5,4] [3u+S,31 [2u+K,S] [3iH-7,3] [2u+7, 6] 



2 2 



[2p+2 l,p 1] [2/>+2u 1, 



... cos. (2u 5) I 



[2iH-l,2J [2+5, l][2il+5,5] [2+S, 2] [gu+S, 4] [2u+7,5] [2tt+7, 



"'V?^; "" *! c 3 - ( 2 -3) - 



[2u-M,l] [2u-l-3,l][2+3,2] [2u+8, 2] [2u+5, 3] [2l+7,3] [2u+7,4] 



" 



[2o+2 l,p l][2p + 2 l, 

 + -- + .- - 



,l][2+5,l] [2ll+5,2][2+S,2] [3it+7,3] [3n+7,S] 



l,p] ) 



^ + - 



+ > 



[2+2u !,!] [2p+2 J,p 1] j 



+ U ^ 2 V + *-3 - ! -+... cos.(2+l)x 



[3iH-3,l][3u+5,0] [3u+5,3][3iH-B,13 [2tH-7, 3] [2u+7, 2] 

 + * + 9 4 + 13 



___ 

 [ 



[3iM-S,3][3iH-S,0] [2+7,5][2tH-7,l] 



+ 13 



s 



[2u--7,3] [2+7,0] 



2 P + - .' 



Etc., etc. 



x H-elc. 



