Iiincqiie obrinebimus iftam aeqiiationem dififerentio- difFc- 

 rentinlcm : 



ddp- P Idj^ + <?$- Jm .^*) A (b cj r.^ 4- p) I B (^ co( . ^ - p) 



' ^ d T- — . V' ~ u' 



§. 19. Nunc fi denuo haec fi t combinatio: 

 ddq fin.^- ddj cof. ^ co{. (p ^ d d z cof.^ fin.<p; 

 confijquemur pro ifl:a exprcffione: 



ddpfin.^coC^-^dpd^Cm.^^~pdd^{'w.i^'--p(i^'C\n.^cof.^ 

 - ddp fin.<^ cof.^ - 2 dpd^ coc'r;~pddt^' coi.^' 

 ■\-pd^' fin. (^<:oC.t,-\-pd c|)'- fin. r, cof. ^ 

 -- zdp d^-pdd^-Jt-pda^f fin. <^cor. <; 



vnde hanc obtinemus aequationem difFerentio-difFcren 

 tialem : 



pdd? -4- .dpd^^pd(p^- Jm.^coJ.i — ^ fin /( l^ — ^). 



Tum vero quia efl: 



dy -^ d z'' nz d iv' -\- IV' d (p' ; erit 

 d q^- -\- dy' -^-dz^ — dq' -^ d zv' -H iv' d (p* 

 — dp^-\- p' d ^' H- w^- d Cp'- , 



idcoquc ob 



pix-^dy-^ iz.'^ _ dq^-f-a>»-<-d g^ __ r, M _i_ 1 4- £\- fiet 



Ap^-^p'-di^-^io'd(p * — 2 CA _i- 1 -4- £ ) , 

 d T^ ^l) ~ u ' a •' 



Hlnc fi aequatio differentio- differcntialis §. fiiperiori in- 

 vcnta per p multiplicetur ct ad pioduflum aequatio vlti- 

 mo loco inuenta addatur, ifta prcdibit aeqiiatio: 



pidp -t- dp->- — _ A /) ILf^C ztij ^ B fi 'shjsliLnJ^ 



Cac- 



