Question

△ABC的周长为41cm,BC=9cm,AD平分∠BAC,S△ABD:△ACD=5:3,求AB,AC的长

Answer 1

由题可知,AD为∠BAC,作DE⊥AB,DF⊥AC,则DE=DF

△ABD:△ACD=5:3,即（1/2AB*DE）:(1/2AC*DF)=5:3

也就是AB:AC=5:3,AB=5/3AC

AB+AC+BC=41即 5/3AC+AC+9=41

所以

AB=20,AC=12