[ * 9 ® ] 
In hoc cafu enim a A = A b, b'B — Bc, cC — Cd , 
d D = D 6c /> P — P y, q (V== Qr, r R — R s, 
sS — Sp 6c confequenter A : A b : : p P : P q 6c 
b B : B c : : y Qj^ Q & ^ 1C deinceps • ergo per the- 
orema haec duo parallelogramma erunt inter fe aequalia, 
quae eft notiftima ellipieos proprietas. 
Idem did poteft de polygonis inter conjugatas hy- 
perbolas eodern modo defcriptis. 
T H E O R. V. 
Rotetur conica fedio circa diametrum ejus (A L), 
✓ 
6c fit MAM, 6cc. folidum exinde generatum j fint 
fq> rs > st > tv, v w, wp, 6cc. [Fig. 6.] lineae, 
quae tangant folidum in refpedivis pundis P, Q, R, S, 
T, V, W, 6cc. 6c erit contentum 
p P x q Qx rRx^Sx/T xvV x w\V x 6cc. ~ 
Pyx QV x Rj xS^xT'uxVw x 6cc. 
T H E O R. VI. 
Sit ellipfis APB QC R, 6cc. rotetur circa diame- 
trum ejus BD; & circa conjugatas diametros (AC 
6c BD, PR & QS) defcribantur elliptici cylindri 
(pqr s 6c acbd ) [Fig. 7.] folidum generatum cir- 
cumfcribentes, 6c erunt hi duo cylindri inter fe ae- 
quales. 
Sint duo folida e truncatis conis compoftta, folidum 
generatum circumfcribentibus, 6c quorum latera con- 
tinue 
