17 
Here also + must describe in its complex plane the imaginary axis. 
For a,,= 0, we get (2a,,‚zta,,y) y + a,, = 0. 
A solution of this is given by- 
—l 
he OE | (a, „et +5 A330 6) 
20,4 
U er. 
Here also only purely imaginary values of + come in consideration, 
as might be expected. 
The second case of degeneration (IV) presents itself for 2 — 0, 
i. e. Jd, = + 1. Here we must distinguish three subdivisional cases, viz. 
I1V*. a,, =90: the point O lies on the conic, 
IV. A,,; = 09: the conic is a parabola, 
BES ay = 0 and=A,,— 0: the point: 0 lies on the: parabola. 
ase 1V*. Here we have (70a) (4 comm. p. 1017); substitution 
of t, =0 furnishes 
I=, an en ESO) 
SO 
3 
WIS 
pee 
V2 
Now the equations (62) and (63) (4 comm. p. 1015) teach us 
2Alz 2hz | 
33 ee 5 
V2 
en 4A? j 4f\? 1 
A,,«-A,,y=V-A,,9? +2092 = SS SS 2 
re Tt et tT 
has hm 
° 2 V2 
T 
‘ 
aA ETT 
93 oe 
V2 
so we get 
22 (4 id VA F Tt ) 
—— 18 1 %33 a¢,° 86 
Ah ee 
V2 
5 (89) 
z Tt 
. (men A, ‚sh Za) 
A, ch? —— We 
Y2 
Proceedings Royal Acad. Amsterdam. Vol. XV. 
