242 



S z=z pqr V p q -i- pr -\- qr 

 atque prima conditio pro rationalitate perpendiculoruai 

 A, B, C, postulat ut sit : 



pq~^pr~hqrz=zQ. 

 §. 4. Pro altéra conditione rectarum a, p, y* angU- 

 los bisecantium , cum sit : 



Vbc (b -^ c -\- a) (i ■+- c — g) ^ 



a ô~4^"S "~* 



/j >^ a c (a -f- c -f- t) (° + g — fc) , 



H Th- c > 



y a 6 (a -f- & -f- c) (a + & — g) . 



y — r^- 2i f 



statuatur , ut supra fecimus : 



ï. h -\~ c — a z=. Qf; 



II. o-f-c — b z=: 2 ^; 

 III. a-f-6 — c z=: 2 h; 

 ita ut sit, addendo II et III, I et III, I et II : 



a =: g -h h = qr + pr; 



h z^ f -h h — pq -\- pr; 



Cz^f-\-g~pq-^ qr; 

 quibus substitutis habebimus ; 



gfqV' (p-^r)( . 7-t-r-)(y.7-f'j>r-f-<7r )' , 



if 9 -t- pr -4- çr ■'' 



O agry (f> + ^Kf> - hrJC-7 '--f- p?-l-f>r) . 



Y •~'~ i^pr -i- qr -H pq 



f. 5. Cum auteiH prior conditio jam postula verit ut sit: 

 pq -^ pr ^ qr =:. U, 

 ponatur hoc quadratum ; 



