^ftdX + fndY=:dycoCA — dzf\n.icoC.r 



+ (i-}-x) {drcoC.^-^-d^ (i - fin. t* fin. t-') 

 — y d Q, fin. i' fin. r cof. r — 2 ^ ^ fin. ( cof i fin. r 

 pro tertia autem parte pariter iam fupra inuenimus : 

 — w/X — «Y — 2fm. ifin..r — — ( i-\-x) 

 uX — yY — —{i'\-x) cof i-hsfm.ifin.r 

 ' _iM X - « Y = - (i +x ) -f 2 fin. i fin. r =-(i+ji:)(i -fin.t*fin.r') 



-j-j' fin. t* fin. r cof r + z fin. i cof. i fin. r 

 His igitur coUigendis erit 



fix^ , /111^-+=^^'^^ -2^^^2:fin.icof.r+(i+:»:yrV, 



{,n}-\-[^^^)-^^^^djcof.i +2{i+x)drd^cr.i 



-{i+x)d^^Cui'{i.r' 

 —y dQ; fin. i' fin. r cof r-z dQ'' fm.di cof icof r 

 his igitur rerminis ad finiftram translatis aequatio prodit: 

 ddx - 2 ^r r/j+a r^dz fin.icof r-( i+x^dr^' 



-zd^dycof.i -2{i+x)drdQcoCi 



, -{i+x)d^' 



+ {i +x) dQ; fin. i' fin. r^ + r rt'^' fin. i' fin. r cof r 

 -i-z^^'fin.icof ifin.r — (wL + «M + Nfin.ifin.rl</f* 

 quae cum praecedente §. 10. exhibita prorfus congriiit. 



§. 15. Deinde cum altera nofira aequatio fuerit 

 ^ — _ V X - |ji Y -f- 2 fin. I cof r 

 erit pariter bis diffcrentiando 



ddy~ — vddX — ^xddY + ddZ fin. i.cof, f,;,^ -„ j,,(.T ) 

 -2dXd\^{—2dY 1^-2 rfZ^r fin. ifiq. r (II ) 

 -X^^v-Y^^[Ji-2^r'fm.i"cof.V- -'-[111) 

 quae fingulae partes euoiutae pracbcnt 



(1) </;'(-yL — jjiM-f-Nfin.icof r 



' (11) 2(yr(-wf</X-«^Y-^2fin.ifin.r) 



+ 2d^{ + ixdX-yd\) 



