4t 



^^--a et |^- = S. Hinc ergo ûci 



l^= a(t) ^ S (1^ ev g^ a(î^) -^ S (^). 

 Deinde erit -,^ a . ^^J :^ a (|tf ) -f- S (/Ai) 



quibus colleclis fiet : ' -t~'<i'î)-' 



(p) = a-^i^D + ûQ- (!?#) + as (3^.) 



sive concinnius : . -'' 



33» dQ_ /3z\ . 3S /3sv 



3^ 33- ^dl) i"" 33' ^3u/ 



4-aa(|^rT + 2 as G^y + ss @ . 



§. 9. Istos jam valores pro formulis ditTerentialibus 

 secimdi gradus inventos heic uni obtutui exponamiis : 



■*• \dx^) 3i V37 ^ "^ 3 X V3u/ 



+ PP(^4!) + 2 PR (^^J ^- RR (1-^) , 



-»T /332\ 3P /3z\ I 3R /3z\ 



■^^* \dxdy) dy \dtf "1" dy \du) 



4- Pa(^43 + (PS + aR) Cù) -H i^s O. 



ITT /^^^ — ^Q-/'^_5\_i_ 9 s /32s 

 •* V3j2/ 33, V(J f/ "1 3> \3u/ 



4-QÛ(^)-K 2aS(^),+ SS(^^!), 



quibus jungantur formulae dificrcnLiales primi gradus 



(aS = P (';) + R (aD 

 (ai) = Û(Vp-f'sO. 



