— 489 



7„_m=»*'„_m+,cosa„_„, = 



(33) \ ''■' I"'"*'", sc fosse 



[7^cos-^«„_,cos*a„_j . . . cos^a,,.^^, 



|— 2j,(s„senp,.cos^«„_ cos««„_, . . . cos^a 



■ •"'..-,senp„_,cosV,_2CosV,_3 . . . cos*« , 



'^"-i — *"-2 = ■ . . = «„_„,(= a) , 



divorebbc 



y„_». = ?«„_„.+,cosa = [72„cos2""-"« — 2</(s„sen?„cos2'"-«'« 



• • ' -r- . . . -t- s„_„,^,sen9)„_,„^j)j.cosa 



Con queste medcsime sostituzioni avremo dalla (28) le 



/ / [(7'„cosX_iCosa^,_2 . . . cos^'a. 



(3i) 



|— 2jf(s„senp„cosV,_,cos2«„_5, . . . cos^a^. 



s«-,seDp„_,cosV,_2Cos2a„_3 . . . cos'^a^ 



■ . . . -t- s^seu5),)j:cosa, , 

 7, = w^cosx =[7\cos2"-2'« _ 2</(s„seijy„cos2"-»a 



-H s„_jSenf„_jCos2"'-3'« -+- . . . -^ s^scD?^)]'cosct . 

 Dalla (29) le 



[ [V^,cos'^a„_,cosV_2...cosV,_,. 

 ,o g^^ ., )-2ry(s»senp„cos^a„_jCosV_,...cos2«„_ 



i-+-s„_,sen9„_,cosV,_2Cos''a„_,...cos^a„_„ 



-*-••• -1- s„_,^senj)„_„)]: , 



w^.m = (7'^-._m — 23s,_„sen?„_„.)"' == [/^cos^'-a — 23(.s„sen?„cos«'"a 



-t- s„-,senp„_,cos2""-i'« -+-... ^- s„.„.sen9„_.)]! . 



65 



