Afiother 7)ETERMINATI0N. 
Draw A Y parallel to M N, and A Z parallel to 
MV : then is the Angle under YAZ, equal to that 
under L M N, which is equal to that under L C A ; 
whence the Arches A L, Y ^ are equal ; but the 
Arches A L, V Z are likewife equal, becaufe LV, AZ 
are parallel, therefore Y V being joined, and L r drawn 
perpendicular to A C, the Chord V Y ihall be the 
double of L r ; but V A being likewife let fall per- 
pendicular to AC, becaufe M V is the double of M L, 
V A iliall be the double of L r ; and therefore V A 
and V Y fliall be equal ; whence the point V lhall be 
in a Parabola, whole Focus is the Point Y, its Axis 
perpendicular to A C, and the Latus re6fum^ belong- 
ing to that Axis, equal to twice the perpendicular let 
fail from Y upon A C But if K V be joined, the 
; Vide de la Hire Sed. Conic. lib. 8. prop. 1,3. 
Angle 
