ΔDBC - dreptunghic } => ∡D = 30°
∡C = 60°
Ducem EB ⊥ DC
In ΔDEB
tg30° = EB/DE
√3/3 = 4√3/DE => DE = 12√3/√3 = 12 cm
In ΔBEC
ctg60° = EC/DE
√3/3 = EC/EB => EC = 4√3·√3/3 = 12/3 = 4 cm
DC = DE + EC = 12 + 4 = 16 cm
AB = DE = 4 cm
Lm = (DC + AB)/2 = (16 + 12)/2 = 28/2 = 14 cm
