Barrow, Isaac
,
Lectiones opticae & geometricae : in quibus phaenomenon opticorum genuinae rationes investigantur, ac exponuntur: et generalia curvarum linearum symptomata declarantur
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<
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xml:space
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<
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xml:space
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tali _Theoremate_ continetur: </
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<
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xml:space
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">Si ad rectam aliquam lineam (hoc eſt
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ad cjus ſingula quæque puncta) applicentur rectæ lineæ parallelæ, ad
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note-0216-01
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xml:space
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">Fig. 23, 24.</
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rectam AD conſimiliter diviſam applicatarum differentiis proportio-
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nales, reſultantis hinc plani ad parallelogrammum æque altum, ad
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eandémque baſin poſitum, rectarum AP, TP proportionem exhi-
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bebit. </
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<
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echoid-s9292
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xml:space
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">Ut ſi rectæ AD, α δ ſimiliter (in partes ſcilicet æquales in-
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definitè multas) dividantur; </
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<
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xml:space
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">& </
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<
s
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xml:space
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">rectæ β μ, γ μ, δ μ rectis BM, NM,
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OM (quæ differentiæ ſunt rectarum ad AD applicatarum, incipi-
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endo à puncto A) proportionales ſint, erit ut figura α δ μ ad paral-
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lelogrammum α
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δ μ φ, ita AP ad TP. </
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<
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xml:space
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">Cum enim recta quæpiam
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ex applicatis ad AD; </
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<
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<
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">g._ </
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<
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">DM æquetur omnibus ſeipsâ mi-
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norum differentiis (ipſis nempe BM, NM, OM) & </
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<
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α δ μ conſtituatur è rectis β μ, γ μ δ μ eâdem proportione creſcen-
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tibus; </
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<
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<
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<
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xml:space
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">ei reſpondens
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trilineum α γ μ quaſi conflatur è parallelis β μ, γ μ pari ratione
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creſcentibus; </
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<
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">hoc ſemper eveniat; </
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<
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xml:space
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">omnino patet trilinea α δ μ,
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α γ μ, α β μ rectis DM, CM, BM proportionari; </
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<
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xml:space
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modum hunc in priorem recidere; </
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<
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<
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autem hic rectas β μ, γ μ, δ μ velocitates repræſentare, quas pun-
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ctum mobile curvam delineans obtinet in reſpectivis ejus punctis M;
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</
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<
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<
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">trilinea α β μ, α γ μ, α δ μ velocitates aggregatas exhibent ab
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initio ad definita reſpectiva temporis inſtantia; </
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<
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xml:space
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præmonitum) reſpondentia ſpatia BM, CM, DM proportionantur.</
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<
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">E ſupradictis porrò conſectatur, quòd ſi _Circulus,_
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_Ellipſis_, ejuſmodíque curvæ recurrentes hoc progenitæ concipiantur
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modo, punctum eas deſcribens infinitam in recursûs puncto veloci-
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tatem habebit. </
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<
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<
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tangens TM diametro AZ eſt parallela, nec illa proinde cum hac
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niſi ad infinitam diſtantiam convenit; </
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<
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xml:space
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tatem uniformis motûs per AY ſe habebit, ut infinita recta ad ipſam
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PM; </
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<
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<
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quoad hujuſmodi curvas; </
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atas (quales _parabolæ & </
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<
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">byperbolæ_) deſcendentis puncti velocitas in
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quovis deſignato curvæ puncto finita eſt. </
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<
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propoſitæ curvæ proprietates exponendas progrediamur.</
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