l62 



quare 



rp^ -j/ a^dxf __ -— z V {m- + n^) dv" — dz' . 



et dz* z:r m'd/^-f- 'l'cïx^ H- 2mnfZxrf/, 



hinc {nf + «*) rfz^^ — d%^ =r (md!x — mc//)^ adeoque 



rp/-w « (widj: — ndy) 



dz V TnP- -f- rfi 



Ex triangulis autem siniilibus TOM et TMW habebitur 



MW = ï!4^^^E? adeoque 

 sin. MWN = ^ = £-7êEi^ " 



COS. MWN iz: -^ TT r\ il z > 



quum autem sit 



(iH-m^-t-n-^) ds""- ds^^m''dx^'+-n^dx^-i-m^dy-^n^dy^-hm^dz'^^n^d%'^ 

 çt {mdx — nd/Y ziz mVZx= + n^d/^ — 2 mndxdy , erit 

 (1 -4- m'' -i- n-) d^'^ — {mdx — ndx)^ zz d^^ _^ (1 -+- m^ -t- n^) dz% 

 ^ hincqiie 



COS. MWN =: ^^^^Ï±I^^£^^I^ et 



ds y 1 H- to2 -4- ii2 



NW zz MW COS. MWN — ^Vds-^{r^v^^~^n-)à^- 



mdx — ndy 



Unde eraetur 



COS. ONW z= ^ z= — ' ^É.'izzJlÉy. 



? 



et 



^1 ^^ y to2 -h n». y ds^ -t- (1 + m^ H- n^) dz= 



sin. ONW ZZ ^' C^^'-^- ^') (^^^ h- ( i h- m' -h n ^) d^^) — {mdx — M>)' 



Vm^-hn'^ V ds^ + (ï H- "i- 4- i^) <**' 



