Ducem CE perpendicular pe AB.
CE=AD
In Δ CEB (dreptunghic in E) :
mas. ungh.C = 30 gr
EB=AB-DC =9-5=4
cf.Teoremei ungh.de 30 gr :
EB= BC/2 ⇒ BC = 2 EB =8
CE²=BC²-EB²
CE²=64-16
CE²=48
CE=2√3
AD=CE=2√3
A= (B+b) × h / 2= (AB + DC) × AD /2 = (9+5) × 2√3 / 2 = 14√3 cm²
