vezi figura BE=AF= h (inaltimi in trapezul isoscel ABCD) ABEF=DREPTUNGHI ΔADF=ΔBEC⇒DE=EC=(DC-EF)/2=(24-12)/2=6 in Δ dreptunghic BEC⇒ cf pitagora BE²=BC²-EC²=10²-6²=100-36 BE=8 in Δ dreptunghic AFC⇒AC²=AF²+FC²=8²+18²=64+324=388 AC=DB=D (diag trap)=√388=2√97