lo-ii. EXGERPTA MaTHEMATICA. }lj
IDE =» V- -^V' -:-:r' + ^'rr + 4*r-,
FA ^ 4^^J'+ ^t>aj + aax
& CF per ER eft ad FR per CE, vt a - 2 ^ ad a + 2 Z». 5 (4) Sitnunc AR^-a, AB ^ b, AC ^c,BE^ b +y:
ER 3o J^r — g-T + 4fr.r -^ aa + ac
a + c '
CE =» "^'^->^~ ^'^y + ^^y 4- ac + ce
r\\ jayr — ^cyy + ^byx + 3jjr + 3cc^— 2<acj'-f 4(if'j' — 4ci'>' ^^ '*' aa+ijc + cc ^
^"^ ^ 3aa + icc—iac-\-4ab—4be + ^ay-\-i6by — &cy '
��•o XI.
Earvm Descriptio et Tactio*
Datis tribus pundis, A, B, C, quaerilur linea cujus ope radij omnes, in vitro difpofiti tanquam fi venirent à pundo A, difponantur egrediendo ejus ruperficiem,
i5 cujus vertex fit in pundo C, tanquam fi venirent à
pundo B, vel fi tenderent verfus B ; vel denique vt
radij, in aère difpofiti tanquam fi venirent à pundo A,
difponantur in vitro tanquam fi venirent à pundo B.
I. Cadat pundum B inter A & C; & F, cenirum
20 circuli tangentis curvam, cadat inter A & B, fi fiât AE^a-j, &BE=ocj + ^, erit FA ad FB vt — j + a ad ccy + bc; hoc eft, inclinatio radij AE in vitro ad
Œuvres. V. 4"
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