^. ai. Qiioniani igimr pro qiialibet foimula inte- 

 grali geminos adcpti (limus valores , iis intcr fe aequatis 

 impetrabunus fequcntcs aequationes: 



Pdv— CLJ I Rdx—PJz . 



Qdjc — Pdy Rdy — Q.dz . 



-r — p » 



Rdy — Q.iz _ ?d z — R dx 



— r — - 1 



qnae onines trcs , ob pdx-\-qdy-\-rdz — Oy reuocantnr ad 

 hanc vnicam: P/> + Q^+ R mo. In hac ergo aequatione 

 iam infigtiis Hatus aequilibrii continetni- proprietas; neque 

 tamen ea ftatus aequiiibrii penitus exhauritur, fed infuper 

 alia aequatione eft opus ad fohitionem completam pcrfi- 

 ciendam. 



§. zi, Hunc in finem accipiatur pro lubitu unus 

 valor cuiuspiam formulae integrahs, ac prima quidem erat 

 f?ds-=. iiLJl£> "7^'^^- ? qu'ie dcnuo ditfcrentiata lurato ele- 

 mento d s conftante praebet 



X, j ddx(Pdy — (Lix) , dx^P d dy —(H d x) 



r a S — f^, 1 rdi» 



. dx[dP-iy — iQdx) _ dxir[Pdy — Q.J x ) 

 *' rds- rds- ' 



quae per r r d s- muhiplicata ac omnibus terminis ad ean- 

 dem partem translatis abit in hanc formam ; 



ozL~?rrds'-\-rddx(i?dy~(^dx)-\-rdx[?ddy-Qddx) 



■\-rdx{d? dy- d(^d X)- dr dx {? dy--(ld x), 



Tn ifta aequatione littera P ducitur in hanc formulam: 



— rrds^-i-r(^dy ddx-\-dxddy ) — drdxdy^ 

 quae loco r </ jMubftituto valore fit zrdxddy — drdxdy-y 

 at vero littera Q ducitur in drdx^ — irdxddxy'^':^^^ tota 

 haec acquatio per dx diuila erit 



P(2r 



