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

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29097 RG. AG: : _m. n_: : TD. AD & gt; SG. AG. quare 112. _hujus._
_app._
225. _hujus ap._&
gt; SG. unde patet tota AFB extra circulum AEB jacere.
333. _hujus ap._
X. Reliquis itidem ſtantibus, ſiad baſin GE (utcunque parallelam
44Fig. 139. ipſi DB) &
axem AD conſtituta intelligatur _paraboliformis_ ejuſdem cum
ipſa AFB generis (nempe cujus etiam exponens {_n_/_m_}) illa ad partes A
ſupra GE, extra _circulum_ tota jacebit.
Nam in arcu AE accepto quocunque puncto M, ductâque MP ad
EG parallelâ, &
MV circulum tangente; eſt VP. AP & lt; SG.
AG & lt; RG. AG: : _m. n_; itaque rurſus liquet 553. _hujus ap._tum.
XI. Conſectatur etiam dictam (ipſi AFB coordinatam & ad ba-
ſin GE conſtitutam) _paraboliformem_ infra GE ad DB protractam,
66Fig. 139. eatenus intra _Circulum_ totam cadere,
Quòd intra _Circulum_ ſtatim infra EG cadet ex eo patet, quòd ipſam
tangens RE circulum ſecat (quia nempe SE circulum tangit).
quòd
alibi _Circulo_ non occurret hinc patet;
quoniam poſito quòd occurrat
uſpiam ad N, tota ſupra N extra circulum caderet, contra 773. _hujus ap._ modò dictum ac oſtenſum eſt.
XII. Porrò, _Hyperbolæ_ AEB (cujus centrum C) & _parabolifor-_
88Fig. 140. _mis_ AFB, cujus exponens {_n_/_m_}, communes ſint axis AD, baſis DB;
ſit autem AD = {2 _n_ - _m_/_m_ - _n_} CA; & BT _hyperbolam_ tangat; hæc
quoque _paraboliformem_ AFB continget.
Nam eſt CD. CA: : CA. CT. acindè AD. TA: : CD. CA; inverſéq;
componendo TD. AD: : CA + CD. CD. Verùm ex hypo-
theſi, eſt _m_ - _n_.
2 _n_ - _m_: : CA. CD; adeoque inversè compo-
nendo CA.
CD: : _m_ - _n. n_: & rurſus componendo CA + C D.
CD:
: _m. n._ hoc eſt TD. AD: : _m. n_. unde BT _hyperboliformem_
contingit.
XIII. Hinc rurſu datà ratione ipſius AD ad CA, _paraboliformis_
ad punctum B _bype bolam_ contingens deſignabitur.
nempe ſit AD =
{_s_/_t_} CA;
erit {_n_/_m_} = {_t_ + _s_/2 _t_ + _s_}. Nam hoc ſuppoſito erit

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