Barrow, Isaac, Lectiones opticae & geometricae : in quibus phaenomenon opticorum genuinae rationes investigantur, ac exponuntur: et generalia curvarum linearum symptomata declarantur

Table of contents

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[61.] _Probl_. IV.
[62.] _Probl_. V.
[63.] _Probl_. VI.
[64.] _Probl_. VII
[65.] _Probl_. VIII.
[66.] _Probl_. IX.
[67.] _Probl_. X.
[68.] _Corol. Theor_. I.
[69.] _Theor_. II.
[70.] _Theor_. III.
[71.] _Theor_. IV.
[72.] _Theor_. V.
[73.] _Theor_. VI.
[74.] _Theor_. VII.
[75.] Lect. XIII.
[76.] Æquationum Series prima.
[77.] _Notetur autem_,
[78.] Series ſecunda.
[79.] Not.
[80.] Series tertia.
[81.] Not.
[82.] Not.
[83.] Series quarta.
[84.] Not.
[85.] Series quinta.
[86.] Series ſexta.
[87.] Not.
[88.] Series ſeptima.
[89.] Not.
[90.] Series octava.
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page |< < (61) of 393 > >|
7961 CAN = ang. NCR + NAR. itaque rurſus ang. KXL =
2 ang.
NCR + ang. NAR. liquent igitur quæ propoſita ſunt;
in uſum (ſi fortè) ſequentium. pro quibus itidem hæc proponenda
ſunt.
XIV. Etiam palàm eſt è dictis ipſos reflexos GN, HR directè
11Fig. 83. procurrentes à ſe divergere;
adeóque duntaxat unum hujuſmodi re-
flexum oculi centrum tranſire;
conſequentèr & puncti A tantùm u-
nam à convexo ſpeculo imaginem exhiberi.
XV. _Lemmatia_ 1. Sint quæcunque tria quanta A, P, C; primó-
que ſit A.
B & gt; B. C; dico fore A + C & gt; 2 B. ponatur enim
fore A.
B : : B. E. erit ergò A + E & gt; 2 B. quinetiam erit ergò
B.
E & gt; B. C adeóque C & gt; E. ergo magis A + C & gt; 2 B.
2. Sit (iiſdem adhibitis quantis) ſecundò A + C & lt; 2 B. dico
fore A.
B & lt; B. C. nam ſive dicatur eſſe A. B : : B. C. vel A. B
&
gt; B. C. ſequetur utrobique fore A + C & gt; 2 B; contra hypothe-
ſin.
itaque potiùs eſt A. B & lt; B. C.
XVI. Etiam hoc adjungo. Si duo ſumantur ad eaſdem axi partes
22Fig. 84. (circulíque convexâ parte comprehenſi) ſibimet æquales arcus NR,
R X;
& ducantur rectæ AN, AR, AX; erit ANq + AXq
&
gt; 2 ARq.
Nam ducantur CN, CR, CX; & demittantur ad AC perpen-
diculares NE, RF, X G;
ſint item NP, RQ ad AC parallelæ
ducantúrque ſubtenſæ NR, RX.
; & quoniam ang. RXQ & gt;
ang. NRP; patet eſſe R X. RQ & lt; NR. NP; adeóque cum
RX = NR, erit RQ &
gt; NP; hoc eſt FG & gt; EF. ergò 2 CF
&
gt; CE + CG; unde 4 AC x CF & gt; 2 AC x CE + 2 AC x
CG atqui eſt ANq = ACq + CNq - 2 AC x CE.
& AXq
= ACq + CNq - 2 AC x CG.
& 2 ARq = 2 ACq +
2 CNq - 4 AC x CF.
ergo ANq + AXq & gt; 2 ARq.
Addo, ſequentium gratià, ſi punctum A ſumatur ad alteras (inſra
centrum) partes;
& reliqua ſimiliter apparentur; fore contrà, tum
ANq + AXq &
lt; 2 ARq. nam in eo caſu eſt ANq + AXq
= 2 ACq + 2 CNq + 2 AC x CE + 2 AC x CG.
&
2 ARq = 2 ACq + 2 CNq + 4 AC x CF.
unde liquet pro-
poſitum.
XVII. Sint jam ad eaſdem axis partes duo quilibet æquales

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