==('59) 



His igitur fubftitutis erit radius ofculi 



Quod fi igitur ftatuatur Xro, habebitur radius ofculi in ver- 

 tice Arr|p. Sin autem ponatur Xzrrip, innotefcit radiiis 

 ofculi in pundo D — 3 p. Denique habebitur radius ofculi 

 in nodo vel pundo interfeclionis B, ponendo Xzrzlpy quo 

 fado fiet Rrz: i2p. 



Corollarium 7. 



§. II. Quod fi i:im pundum Z noftrae curuac ad axcm 

 EF referamus, ftatuendo abfcilfam D V rz .v et appJicatam 

 VZzrzy, erit Xrr|p-}-j' et Y=zp — .r, vnde aequatio 

 ad curuam erit : 



^ = p^ ^^ V(PP-^l py)' 



Du(fla iam ex pundo Z normali Z N, quae axi abfciflarum pro- 

 dudae occurrat in N, erit difTerentia inter recftam D N et ar- 

 cum D Z vbique aequalis femiparametro Parabolae genitricis 

 ter fumto. Cum enim fit diffcrentiando 



:v y ^Y 



d jr ~ : , 



^V^P^lpy) 



erit Subnormalis 



VNz=:^z=:3/(PpH-iPj), 

 ideoque 



D -^ = X -\- :i y {p p -\-lp y). 

 Tum vero erit arcus 



^^ ^ J ^V{pp-+-lpy) 



A a 3 hoc 



