50 METHODVS NOVA CALCVLVM 



25. Quodfi ergo huiusmodi formulac intcgra- 

 \'% ff\ d X (iy variatio quacri debcat , vbi V deno- 

 tat expreffioncm quamcunque vcl primi vel (ecundi 

 gcneris , cx (uperioribus (lUis li^uct hanc Nariatio- 

 neni ita expreflum iri : 

 dtff{yi)dxdy 



quae forma iterum efl: integralis duplicata et prouti 

 vel X vcl y priore integratione vt conilans ipcda- 

 tur , ca tormula vel lioc modo 

 dtjdxf{'JL)dy, 



"vel hoc modo 



^tfdyf['^,)dx 



cxhiberi potefl. 



2fi. Sit nunc V tah's cxprcJTio qualcm fupra 

 § 19 delcripfimus et cuius vaiiationem Icu valorem 

 (^) in § 23 euoluimus , tantum opus ent , fin- 

 gula membra ibi expofita hcic loco (^) «iibllituere ; 

 vnde fequens congcries formularum integraiium na- 

 fcerur , quibus iuncftim luiutis variatio quaefiia 

 d t ffi^) d xdy exprimctur : 

 dtjrN{'^)dxdj'-Vdtjr?^'^;;dx.dj-Vdtj[f(Q_ {^,l)dxdj-\ diJ/R (/^r?dxdy 

 +dtjrP\ij^^)dxdy+dtJJ-(^ {£^^)dxdy^diJJ-K' ij^,)dxdy 

 -^dtl^ ^^.^,)dxdj-\dij] K" ,^,,dxdy 

 -ydij/ix"'i^^)dxdy 

 etc, 

 ?7. 



