Barrow, Isaac
,
Lectiones opticae & geometricae : in quibus phaenomenon opticorum genuinae rationes investigantur, ac exponuntur: et generalia curvarum linearum symptomata declarantur
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ctum. </
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<
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">His utcunque majoris evidentiæ cauſâ, prælibatis, ad corolla-
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ria quæ diximus expromenda nos conferemus è veſtigio.</
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<
s
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xml:space
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">II. </
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<
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parallelos, aut ab eodem puncto divergentes (velin idem convergen-
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tes) & </
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<
s
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">huic vel illi ſingulari, quæ tractanda veniet, ſuperficiei inciden-
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tes (radios, ſingularia quotvis inflexos deſignandi compendia, radia-
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tionibus organicè examinandis profutura, tradituri) generales nunc
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aliquos incidenti cuivis propoſito competentem inflexum aſſignandi
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modos proponemus; </
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<
s
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xml:space
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">quorum adhiberi poſſit, qui rei natæ videbitur
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accommodatior. </
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<
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">Pro reflectione. </
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<
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<
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xml:space
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B ducatur QB reflectenti perpendicularis; </
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<
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xml:space
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">& </
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<
s
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">fiat ang. </
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<
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xml:space
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">_a_ BQ = ang.
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</
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<
s
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xml:space
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">ABQ, vel per B ducta ſit EF reflectentem tangens; </
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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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">fiat ang. </
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a BF = ang. </
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<
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<
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">liquetque factum eſſe, modo utrovis, quod
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xml:space
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">Fig. 16.
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Fig. 17, 18,
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19.</
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requirebatur, Pro refractione vero; </
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<
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pendicularis, & </
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<
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">ſuper diametrum (in hac liberè ſumptam) QB de-
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ſcribatur ſemicirculus, incidentem AB ſecans in R; </
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QR, factóque I. </
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">T (terminis autem I, R hìc & </
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<
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perpetuò proportio refractiones metiens indignitatur) circulo QRB
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adaptetur QS ipſam T exæquans; </
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<
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">erit connexa SB protracta nempe)
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incidentis AB refracta. </
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">? </
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<
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">perincidentiæ punctum B ducatur EF
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refringentem contingens; </
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<
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xml:space
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">& </
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<
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">in hac utcunque ſumpta BK ſit circuli
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diameter, incidentem AB ſecantis ad R; </
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<
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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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<
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In ipſa AB ſumptâ utcunque diametro RB, ſuper hac deſcriptus cir-
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culus ſecet perpendicularem QB ad Q; </
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fiátque I. </
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<
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">& </
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<
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<
s
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dentis AB refractus. </
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<
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modum eſt manifeſta. </
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<
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<
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evadet.</
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</
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<
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">Hoc plerique, diverſè paullò prolatum, accipiunt, aut poſtulant.
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</
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<
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<
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_Herig. Catop_.
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_Axiom._ 2.</
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è præmiſtis autem facillimè colligitur. </
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<
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(ſicut & </
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<
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">nonnulla quæ ſequentur) quàm quia res meretur, oſtende-
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mus. </
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<
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<
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<
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xlink:label
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in B _a_; </
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<
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AB incidens reflectitur in B _a_, erit ang. </
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<
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</
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<
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">Poſito jam _a_ B incidere, etiam angulus quem facit ejus reflexus cum
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BE æquabitur angulo _a_ BF; </
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<
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quare BA ipſius _a_ B reflexus erit.</
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