慜>>705掶惓丅妵屖偑敳偗偨丅

仮CAB佷仮CED傛傝丄
DE=3/2丄CE=7/2丄BE=8-7/2=9/2
B傪婲揰偵儊僱儔僂僗偺掕棟傛傝丄
(BE/EC)(CD/DA)(AF/FB)=1
(9/7)(4/3){AF/(AF+3)}=1
12AF=7(AF+3)
AF=21/5
摨條偵F傪婲揰偵儊僱儔僂僗偺掕棟傛傝丄
(FA/AB)(BC/CE)(ED/DF)=1
{(21/5)/3}{8/(7/2)}{(3/2)/DF}=1
21񓉣=5񑧋DF
DF=24/5