Barrow, Isaac
,
Lectiones opticae & geometricae : in quibus phaenomenon opticorum genuinae rationes investigantur, ac exponuntur: et generalia curvarum linearum symptomata declarantur
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CN + DB. </
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<
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<
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<
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eſt DB x DC. </
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<
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xml:space
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<
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xml:space
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<
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<
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xml:space
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DC q = CN x P; </
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<
s
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xml:space
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">ergò patet _curvam_ DNN _eſſe parabolam_, cu-
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jus _parameter_ P, _vertex_ D; </
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<
s
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xml:space
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">_diameter_ ipſi BA parallela.</
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<
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<
s
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xml:space
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_ à S. </
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xml:space
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Spirali.</
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prolixitate, demonſtratum.</
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<
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DY, ut jam ſemper habeant BE, BC rationem eandem (puta quam
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BD ad R) erunt etiam interſectiones ad _par abolam_.</
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<
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">Nam biſecetur DB in G, ducatúrque GV ad BE parallela, ſe-
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cans curvam DNN in V; </
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">& </
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<
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">quoniam eſt BC. </
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CN. </
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<
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<
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">ergò (ſecundum benè
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notam _parabolæ proprietatem_) eſt curva DNN _parabola_, cujus _para-_
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_meter_ R, _diameter_ GV.</
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<
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<
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ſed ad aliam poſitione datam (DH) feratur parallela; </
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petuò BE. </
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</
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<
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">Nam ductâ NG ad BA parallelâ, nuncupentur DB = _b_. </
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_h_; </
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<
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</
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{_by_/_x_}._</
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{_h_/_b_}_x x_. </
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<
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<
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curva DNN _hyperbola_, quæ ſuprà habetur determinata.</
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jam feratur CX, ut ſemper habeat BE ad BC rationem eandem, quam
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BD ad R; </
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<
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<
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<
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eunte; </
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