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

4426 GP _a_, HP δ ità diſponantur, ut latera PG, PH ſibi congruant (un-
de major angulus GP _a_ minorem HP δ comprehendet) tum centro P
per δ deſcribatur circulus E δ F ipſas PG, P _a_ ſecans punctis F, E; item
connexâ EH, centro H per δ tranſeat circulus HMN ipſas HP, HE
ſecans punctis N, M; denuò connexa E δ cum PG conveniat in L.
Eſtque jam ang. _a_ P δ. ang. δ PH: : ſector EP δ. ſector δ PF & gt;
triang. EP δ. triang. δ PL: : Eδ. δ L : : triang. EH δ. δ HL & gt;
ſector MH δ. ſector δ HN : : ang. EH δ. ang. δ HP. eſt igi-
tur ang. _a_ P δ. ang. δ PH & gt; ang. EH δ. ang. δ HP. ergóque
compoſitè ang. _a_ PG. ang. δ PH & gt; ang. EHP. ang. δ HP. per-
mutandóque ang. _a_ PG. ang. EHP & gt; ang. δ PH. ang. δ HP. eſt
autem HP. PE : : HP. P δ : : I. R : : GP. P _a_. adeoque EH ad
_a_ G parallela; vel ang. EHP = ang. _a_ GP. ergò erit ang. _a_ PG.
ang. _a_ GP & gt; ang. δ PH. ang. δ HP. hoc eſt ang. _a_ BG, _a_ BP
& gt; ang. δ BH. ang. δ BP. vel componendo ang. GBP. ang. _a_ BP
& gt; ang HBP. ang. δ BP. Quod erat demonſtrandum.

_Corol_. 1. Ang. _a_ BG. ang. _a_ BP > ang. δ BH. ang. δ BP.
2. Ang. _a_ BG. ang. PBG > ang. δ BH. PBH.