Barrow, Isaac, Lectiones opticae & geometricae : in quibus phaenomenon opticorum genuinae rationes investigantur, ac exponuntur: et generalia curvarum linearum symptomata declarantur

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28895 ipſam AFB) ſit perpetuo TG major quàm SG; dico nullam cur-
væ AFB partem intra ipſam AEB cadere.
Si fieri poteſt, cadat pars NFM; ità ſcilicet ut curva AFB cur-
vam AEB interſecet punctis M, N;
his autem interjecta concipiatur
indeterminatè ordinata EFG;
ſint verò lineæ LXK, RYQ tales,
utductis rectis EO, FP ad ipſas ES, FT perpendicularibus, protra-
ctâque rectâ EG, ut hæc dictas lineas LK, QR ſecet punctis X, Y;
ſit GX = GO, & GY = GP. Jam ex oſtenſis patet eſſe _ſpatium_
IHKL = {HMq - INq/2} = ſpat.
IHQR; adeóq; ſpat. IHKL, IHQR
æquari.
Verùm ob GE. GO (GX): : SG; GE. & lt; SG. GF & lt; TG. GF: :
GF.
GP (GY) & lt; GE. GY; eſt GX & gt; GY; adeòque (cùm
hoc ubique ſimiliter contingat) ſpatium IHKL majus ſpatio IHQR;

quod repugnat oſtenſo.
itaque liquet Propoſitum.
Hinc tota AFB extra totam AEB jacet, nec illa hane uſquam inter-
ſecat.
IV. Sit curva quæpiam BAE, cujus axis AD, & ad hunc ordina-
11Fig. 135. ta baſis ADE;
ſegmenti verò BAE centrum gravitatis ſit punctum
H, qer quod ducta ſit recta RS ad BE parallela Porrò per puncta
R, S tranſeat altera curva (vel linea quævis) MR ASN, habens iti-
dem axin AD, ac ita priorem curvam BAE ſecans, ut ejuſce pars
ſuperior RKAP Sintra curvam BAE cadat, inferiores verò reliquæ
partes RM, SN extra eandem;
erit ſegmenti MRASN centrum
gravitatis infra punctum H, verſus baſin MN.
Nam è ſegmento RIAO Sablatum RIAK + AOSP reſidu-
um BRKAPSE deprimet verſus baſin BE, puta ut jam ſit hujus
reſidui _Centrum gravitatis_ ad X;
tunc adjunctum BRM + ESN
adhuc totum MRKAPSN magis deprimet;
adeóque centrum ejus
infra X conſiſtet, velut ad Y.
itaque conſtat Propoſitum.
V. _Circulum_ AFB, cujus _Centrum_ C, tangant duæ rectæ BT, E S
22Fig. 136. _Diametro_ CA occurrentes punctis T, S;
& ad CA perpendiculares
ſint rectæ BD, EP;
ſit autem AD major quàm AP; erit TD. AD
&
gt; SP. AP.
Nam eſt CT. CA: : CA. CD. Ideoque CT - CA. CA -
CD:
: CT. CA; hoc eſt TA. AD: : CT. CA. Simili ratione conſtabit
eſſe SA.
AP: : CS. CA. Eſt autem CT. CA & gt; CS. CA.
quare TA, AD & gt; SA. AP. vel componendo TD. AD & gt; SP.
AP.

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