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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fecans in N; </
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<
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">& </
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<
s
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xml:space
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">per N ducatur KN G; </
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<
s
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xml:space
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">hæc ipſius AN reflexa
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erit.</
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<
s
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<
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<
s
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xml:space
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">Nam ob ANq = ACq - Vq. </
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<
s
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xml:space
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">erit Vq = ACq - ANq.
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</
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<
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xml:space
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<
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xlink:label
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xml:space
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">Fig. 89.</
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adeóque CBq. </
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<
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<
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xml:space
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<
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<
s
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<
s
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</
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<
s
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xml:space
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">quod, è præmonſtratis, reflectioni proprium eſt. </
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<
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">ergò liquet pro-
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poſitum.</
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<
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</
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<
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<
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<
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">ltà quidem in hoc caſu; </
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<
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xml:space
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AC &</
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<
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<
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<
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xml:space
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">reliquis ſtantibus, Sumendum erit intervallum AN
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= √ : </
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<
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<
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xml:space
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">ut ſit ANq - ACq = Vq. </
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<
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xml:space
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">ut poſthac
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conſtabit, ubi de concavis agemus. </
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<
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xml:space
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">Aliter hoc idem. </
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<
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<
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<
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<
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">& </
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<
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<
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<
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<
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<
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">E. </
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<
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">ſumatúrque CQ = E
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+ F. </
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<
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xml:space
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">& </
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<
s
xml:id
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xml:space
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">du@ta QN ad AC perpendicularis circulum ſecet in N. </
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<
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connexæ AN, KN altera alterius reflexa erit. </
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<
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liquidò conſectatur. </
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<
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xml:space
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<
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<
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CQ = F - E; </
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<
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<
s
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xml:space
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">(reliquis nihil immutatis, utì poſtmodùm appa-
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rebit) factum erit.</
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<
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<
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<
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">alióſque ſpeciales, ſi qui ſunt, excipiendo, generaliter con-
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ceptum omnino Solidum eſt, & </
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<
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_Geometris_ hactenus attentatum difficilius reperiatur. </
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<
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dem per lineam extrui, explicaríque poterit ſibi peculiarem, hoc vel
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adſimili modo deſcribendam.</
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<
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<
s
xml:id
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xml:space
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">Connexâ CA, ſuper diametrum CA deſcribatur circulus AI C;
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</
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<
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">item ſemidiametro CA deſcribatur alter circulus AH G. </
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<
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educantur rectæ quotvis CI circulum AICſecantes punctis I; </
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<
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A, I ductæ rectæ circulum AHGſecent punctis H; </
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& </
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<
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">X rectæ ducantur ipſas CI decuſſantes punctis N. </
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<
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<
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xlink:label
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">Fig. 90.</
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puncta quævis deſignabilia tranſibit linea, _Problematis_ expoſiti ſo-
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lutioni accommodata. </
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<
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interſectio N (qualium certè pro reflectentis circuli magnitudine ſub-
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inde quatuor, aliquando tres, modò binæ tantùm erunt) & </
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<
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tur AN. </
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<
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">Et quoniam angulus CIA in Semicirculo rectus eſt, erit
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recta AH biſecta in I. </
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<
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">adeóque triangula AN I, HNIſibimet æqua-
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lia prorſus & </
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<
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<
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<
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</
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<
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<
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<
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<
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">Verùm quoniam (ut pridem admonitum) hujuſmodi conſtructi-
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ones, etſi longè faciliores iis quæ per vulgò receptas lineas peraguntur,
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& </
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<
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