erit 



firt iACDcof BCrrcof^ABcor.^BDfin. ABI). 

 Demonftf. Ex polo C ducdntur ad A B, B D, arcus cir- 

 culoiuin maximorum Rormalcs CE, CF, eritque tn tran- 

 gulis redangulis B C E, B C F, fin B C E ={|^J^ 



fmBCF-j;^ er cof.B CEmcof.BE.fin EBC; 

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

 inde colligitur 



fin.ECFr:fin.BCE. co.r BC F + cof.B C E fin. BCF 



^ Jln. B E . col. B P Jin. C B F i Jtn. B F . coj.B E/n.C B E 

 J"i. B C ' Jtn. BC ' 



At quum fit 



tang. E B iz tang. B C cofi E B C ; 



tang. B F ~ tang. B C cof. C B F, 

 vnde quoque habetui' 



Jin. B E eo/. E B ca/. E B C . 



Jin.B C coj. B C * 



his valoribus fufFecSis confequimur 



fin.ECF='-?^J^ (fin EBC cof.FBC + fin.FBCcof.EBC) 



= ^-B^-fi"-EBF, 



ct quum fit 



ECF=:!ACB-|-^BCD 



ob angulos A C 3, B C D bifedlos per arcus E C , F C, 

 fiet quoque ob 



tACD;i:i8o-|ACB-iBCDj 



fin. E C F iz: fin. 1 A C D , 



vnde 



