Tum vero eft 



cof. B C E =: cof. B E (in. E B C; 



cof. B C F = cof. B F fin. C B F, 

 ergo 



cof. E CF = cof.B C Ecof. B CF- fin. BC E . fm. B C F 



=cofBEcofBF(fin.EBCfin.FBC-cof.EBCcofFBC) 

 -fin. BE . fin. BF, 



fiue 



-cof.ECFznfin.BEfin.BF + cofBEcof.BFcofABD; 

 et quum fit 



ECF=:i8o-l ACD, 

 fiet omnino 



cof.^ACD = cof BE.cof.BFH-fin.BEfin.BFcof.ABD. 



§. II. Theorema X. .5'/ bini arcus circujoyum 

 maximorum AB, DE, fe interfecent in F, circulo vero 

 cuidam minori occurrant in A , B , D , E , erit 



tang. i A F . tang. i B F — tang. | D F . tang. l E F. 



Demonjfr. lungatur polus circuli minoris C cum puncflo '^^^- '^^* 

 interfedionis F, arcu circuli maximi CF, et ducantur ar- j^"^j ,5^*2. 

 cus circulorum maximorum CB, CD, eritque in trian- 

 gulis C G F, C H F rertangulis 



cofFG=:Si-^ cof.FH^|L^. 

 Simili modo in tiiangulis CDH, CBG redangulis eft 



cof.DH = gic^, 

 Jcia Acad, Imp. Sc. Tom. Vl. P. /, I pro- 



