din triung ABC <D=90de grade => TP , BC^2 = BD^2+DC^2=> 16=12,8^2+DB^2=> DB=radical din 92,16=>DB=9,6cm
triungABC=><A=60grade => trung ABC echilateral => AD=9,6
triung ABC <B=90grade => TP , AC^2=AB^2+BC^2 =>22,4^2=AB^2+16^2 => AB=radical din 245,76=>AB=15,67
PerimABC=AB+BC+CA=>15,67+22,4+16=54,07