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# Title: Francisci Dulaurens Specimina Mathematica Duobus Libris Comprehensa (shelfmark Leibn. Marg. 134)
# Folio 125, page id 1066520976:0147
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LIBER I. CAPUF V.
DEMDAS, LRATTO EN P CASU.
TFeraque propolicarum rectarum adlecancem perpen-
dicularis est proprer concessam Llorum a propolcis rectis
lineis ad secanrem recticudinem. Ouaproprer sumpris
propolicarum rectarum alcerutra pro lubjecta, ex lecance
pro perpendiculo parallelarum descripeore, punctum in
quo alcera propolitarum rectarum d lecante diridieur,
per conrenientem ipsius secancis, sire dicti perpendicu-
li, Parallelarum descripeoris morionem, rectam lineam
deleribet, alcerilinea, qux pro subjecta Polica est paral-
delam, ex ipsi secanti linex perpendicularem (ex notitia
generationis perpendiculi). Aequi secunda ex proposicis
lineis, per nominacum punctum cransiens, ipsi secanti
perpendiculariter insistie, uc ab hujus demonstrationis
inicio conclusum est, neque ab eodem puncto ad eandem
rectam duo rla dirigi possune (ex probatis ad desinitionem
L.II.) Pgicur recta linea, quam dictum punctum descri-
Dec, eadem omnino est quam propolicarum secunda, e
consequenter illa secunda prima pro subjecta PosItX p2-
xallela eAt.
SECANDUS CASUS. D A TUK.
Tam recta F II, secanS rectaS A B _C CD, internOS, de
ab eadem parre consticuros (1052, _ 3 duobus rectisx-
quales efficiat.
DUSTTUM. DicOAB = CD.
CONSTRUCTTO.
Bilecetur recta F. O in puncto X, a quo in alterueram
parallelarum, uE AB ducacur + lum X P: cum Facto F. R
aequali PO aGATUFX R.