分别过A B做AE⊥X BD⊥X E D为垂足
则BD=2 AE=4 OD=2 OE=1 DE=OD-OE=2-1=1
S△ABC=S梯形ABDE+S△ACE-S△BCD
=1/2(2+4)×1+1/2×5×4-1/2×6×2
= 4