59G ALBERTO LìRAMBJLLA 



e quindi l'equazione 



che rappresenta la conica polare del punto y' rispetto alla 

 curva (3), assumerà la forma : 



( y: IV iv+ iV y; r;+ r; ^v r;+ y:y: Y^){>J:Ml:^-y■ ) 

 +2( y:y:y;-y!y;y:-y;y:y:+y:y:y^) y^y, 



Ma si hanno, per le (4) , 



yIy^y;=. 



- ?/.'■ + //.' + yf- y!\yl-\- yì) + ///(//.'- y'Y- yJy^iyJ-h yì) , 



y;y:y:= 

 y:^-yf+y:'+y:\y:-y!)-y:{y:+ylY-y:y^{y:- ///) , 



,3 ,i 



Y'Y'Y' 



y. + y. - ^j - y, (y. - .v.s )- y, (y. + ^/^ ) + y^ y, (//, — yz ) 



Y'Y'Y^'=z 



-* I -"-2-^3 



'' . f^ l'i.. '% .. ' I .. '\ 



1 I l'i '/ 'l '\l '/ ' ' \l I ' '/ 'l '\ 



- //■ - y. - ^3 + //. {y. + ^3 ) + //. (//2 - //3 ) + y. y^ {y. + y.^ ) 



e (quindi saranno: 



y:y;y;+y^y:y:+y;y:y:^-y:y:y^:= 



— 8 ?/. ?/2 ^3 r 



r; r; r;- r3' r; r/- r ; r/ r;+ r/ f; 1^3'= 

 - F/r/rz+iVr/r' -r/r'r;+r'rTV= 



2 ,1 ', 1 .1 '1 , ', , 2 ' I 2 



-4 2/;V4//;(//3'V?/;^) , 



- Y'Y'Y,'-Y,'Y'Y'+Y,'Y'Y,+ Y'Y,'Y,'= 



-4//;'+4//3'(///V//2'^) • 



