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

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_a_ - {_cc_/_a_} = _x_.
_aa_ - _cc_ = _nn_.
_a_3 - _cca_ = _n_3.
_a_4 - _ccaa_ = _n_4.
Fiat angulus RAI ſemirectus, & Fig. 213in qua AC = _c_; tum utcunque ductâ GZ ad AD parallelâ, ſit
AG (vel GZ).
AC: : AC. ZK, & per K, intra angulum DAR
deſcribatur _hyperbola_ KYK;
tum ſint curvæ CLYHLλ, AMYHMμ,
ANYHN ν tales, ut inter AG (vel GZ) &
GK ſit _media_ GL,
_bimedia_ GM, _trimedia_ GN;
propofito deſervient.
& quo pacto radices reſpectivè
determinantur.

Not.

1. Curvæ CLH, AMH, ANH ad quintam ſeriem pertinent; re-
liquæ HL λ, HM μ, HN ν ad ſextam.
2. ſi A φ = √{ACq/2};
& erit Y communis linearum interſectio, ſeu _no_-
_dus._
3. in tertio ſi fuerit AP = √{ACq/3}, & ordinetur PV,
erit PV maxima(unde radicum una ſemper major eſt quam √{ACq/3}
altera minor) in quarto ſi AQ = √{ACq/4} = {AC/2}, &
ordinetur QX,
erit QX maxima (unde radicum una major erit, altera minor ipsâ
{AC/2}).