PF.RTVRBATI PLANilTARVM. 139 



feii fin.w : fin.w f (/cocof. ojr fin.cr-f/v|/col'crcor w : fin rr 



et diiiidcniio fin. w^rt^ojcof ojr fin.(T-^vpcor.(rcof u:^/v|ycofa-cof w 



"vndc fit rt^ojfin <r— ^/vpfin. ojcof o- leu jtjt^ ~ ,-^|^ 

 prorliis vt antc. 



X. 



Formuhic aiitcm ditfcrcntialcs , antc $. 7. rii- 

 Ycntiic , fi cuohumtur pnicbcnt : 



XdZ — ZdX. dvPcoj. vJ^ Y ni Z — 7. d Y d^// n. v^; 



ZZ jtn.u-jiri.\a ^^ ZZ — jir. a'^ jiv.d 



vndc ob Z.~'-jfin.(rfin.oj nanciscimur has formulas 

 notatu dignas : 



Xrt^Z-Zfl^X — u-y^Cpfin.ucof vjy ct 



Y rt^Z - 2 ^ Y rr c 1' ^Cp fin. u fin. vjy. 



Hinc \t r/Z climincmus , fi priorcm multiplicemi?s 

 per Y poftcriorcm vcro per X, hoc produclum ab 

 illo ablacum rclinquet : 



Z(XrfY-Yr/X)-.r'Vfl'(|)fin.a)(Ycof v|^-Xfin.vi>). 



Cum autcm fit vt vidimus §.7. Ycof \j^ — Xfin. ^sp 



Z co/.ui 



jin, oj 



hacc formula ad infignem fimplicitatcm contrahitur: 

 Xfl' Y - Yrt^X — i"-J^Ct)cof w. 



Hae formulac cum illis , quas IVatim ab initio ia- 

 vcnimus , coniundac fcilicct hiscc : 



XXh-YY^Z2~u^^ ct dX'-\-dY'-{-dZ'-dro' 



S a . in 



