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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IX.</
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<
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<
s
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xml:space
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">Q Ualiter in obverſum Speculi circularis convexum finitè di-
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ſtans punctum radiat, & </
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<
s
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xml:space
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">ubi loci adparet oculo in recta con-
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ſtituto per ipſum radians & </
s
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<
s
xml:id
="
echoid-s3800
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xml:space
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preserve
">ſpeculi centrum trajecta poſtremo con-
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niſi demonſtrare; </
s
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<
s
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echoid-s3801
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xml:space
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">nunc idem quoad aſpectum aliàs ubicunque ſitum
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aggredimur expiſcari. </
s
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<
s
xml:id
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xml:space
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">quò primum attinet ut rectam inveſtigemus,
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in qua conſiſtet Imago; </
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<
s
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">tum ut punctum ejus in iſta recta præciſum
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determinemus. </
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<
s
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">& </
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<
s
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">primo quidem negotio ſatisfactum erit hujuſmodi
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_Prob@ema_ conficiendo; </
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<
s
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">quod (ſequentium quoque gratiâ) genera-
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tim proponimus.</
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<
s
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</
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<
s
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">II. </
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<
s
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">_Dato circulo reflectente_ (cujus centrum C) _datiſque binis pun-_
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_ctis; </
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<
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">ab horum uno recta ducatur, cujus rtflexus per alterum tran-_
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_ſeat._</
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<
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</
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<
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<
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">1. </
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<
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">Si data puncta (puta A, X) ſint ambo in circuli peripheria,
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xlink:label
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note-0081-01
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xml:space
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">Fig. 86.</
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manifeſtum eſt biſecto arcu AX in N, connexiſque ſubtenſis NA,
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N X, rectas NA, NX ſibi mutuò reflexas fore; </
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<
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angulum CNXangulo CNA æquari.</
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</
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<
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<
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">Etiam ſi datorum unum (X) in circumferentia ponatur; </
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<
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">Fig. 87.</
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connexis AX, CX, factóque angulo CXH = CXA, ſore XA,
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XH alterum alterius reflexum.</
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</
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<
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<
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<
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">Fig. 83.</
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nexis rectis AC, XC, biſectóque angulo XCA à recta CN circu-
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lum reflectentem interſecante ad N; </
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<
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">perſpicuum eſt conjunctas rectas
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AN, XN, invicem in ſe reflecti; </
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<
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æquari.</
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</
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<
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<
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">Si puncta data (puta jam A, K) ambo exiſtant in recta per
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reflectentis centrum tranſeunte (nempe AB KC.)</
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<
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<
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<
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<
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">ac inter CB, & </
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<
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media V (unde CBq. </
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<
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<
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<
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<
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<
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">AC). </
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<
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">tum centro A,
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intervallo √:</
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<
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