( 750 ) 
Frobkmi z* Invenire Lineatn Celerrimi Defceftrns. 
SifttBG, CD dux particular infinite parvae in curva qusefita. 
Jam Gurva ilia debet effe talis ut tranfitus a B ad D poft cafum 
a horizontali AQ^fiat in tempore minimo ; quserenduni itaque 
eft pundiim in linea RS (ita ad AQ^ parallela ut differentiae 
ordinatarum GC> DE fint sequales) tale pundum C »nt hoc 
contingat. 
Jam velocitas ejus in pundo G eft i/LC & velocitas in pun- 
BG 
d:o Defti/QDj ^^^^:^/Lc^^ tempus defcenfus per BG, 6c 
etiam--j;^^ eft tempus defcenfus perGD (perProp.liv. pag. 
BG GD 
I j8 Newtoni) Ergo pun<autn Cd^bet effe taleut ^^^'^^^q^ 
— minimo. Supponendo B 8c D effe fixa, fint conftantes 
GCr=DE=m, LC=:b, QD— p ; indcterminatac BG=i=u , 
minimo ; Ergo 
CE=:z; unde - — — + ■ — ^ = 
^/b Vp 
udu zdz 
m — o fed du=— dz<quia v+z=: 
u z 
conftanti) Ergo « — = ZT^i^^^T^ ; unde patet 
bH^m+ 
