••iV 



) 5(^~ { §-?f- 



ouie in § pr.icccdcnri allata funt in \l\\m vocentnr. Cae- 

 ternni fi ad rigoicm Ge«i:r.ctricnin liuiiis dcmonllrationis 

 qnidqnam dcfiderctnr , il!i dcfciftni Inpplondo firrnpnlofius 

 non cft vt inuigilcmu';, qnia mox aliam conlUndionem 

 huins Problcmatis adfcremus; pracmiflb nimirnm 'Ihcorc' 

 mate quodam Gcomctrico admodum cleganti ab 111. Eitlcro 

 primum inuento. 



Thcorcma Gcometriciim. 



Tab. M. §■ 31- Si cx foco F fcclionjs couicac erigatur ad 



^'8- 3- axcm principakin A B normalis F E, qhi ctiruae occurrif 

 in il , et fi ihftper cx foco ad curuam du^lae fucriut inicae 

 quaccuKquc F JV» , FN, tuiiique linea NM producntur, vs- 

 que dum lineae FK, fi opus cjl produ&.ie, occurrat in P 

 et cx P in Hncam F L, quae augulum .\I F N bifecat, dtica- 

 tur mrmalis PR ipfis F .\1 , FN //; m, n occurrcns ^ erit 

 F m — F u, aeiiualis femiparametro piincipali Scciionis co- 

 fiicac. 



Cnm hoc Tiicorcma Gcomi-tricnm variis qnidcm 

 Fationibus dcitionflrari poiJit, tnm illam praccipuc dcnKHi- 

 fintioncm hcic adfcrrc conniiuimus, qnac maximc concin- 

 na vidctnr. Si iyitnr rnpponnntur dii<fl:ic J.incac MT, 

 NU ad rc^ionem couicf^ni normalcs, onac axi principali 

 in punftis T et U occurrant, mmque UX, T V norma- 

 ks ad rccflas FN, F M ; finiili rationc ac fiipra dcmon- 

 ftr.ibitnr cfTe M ^ zr N X acqnalis lcmiparamctro princi- 

 pali ct F T : F M n F U : F N. Dcindc fi ex puncflis M 

 ci N in rc(fram FP nojmaics dcniittantur Ml, NK crit 



A I M F 



'>g- 4 



