a treia = 35 cm - 12 cm - 16cm = 7cm A
12cm 16cm
B E C
BC = 7 cm
AE = bisectoarea ; E ∈ ( BC)
teorema bisectoarei : BE / EC = AB / AC
BE = 7cm - EC
( 7 - EC ) / EC = 12 /16
( 7 - EC) / EC = 3 / 4
4 · ( 7 - EC) = 3EC
28 - 4EC = 3EC ; 28 = 4EC + 3EC ; 28 = 7EC
EC = 28 : 7 = 4 cm
BE = 7 cm - 4 cm = 3cm