已知:A(2,4),B(-3,2),C(3,-4),求S△ABC

问题描述:

已知:A(2,4),B(-3,2),C(3,-4),求S△ABC

过B作直线平行于y轴,作AD垂直于该直线于D,CE垂直于该直线于E,则AD=2-(-3)=5 BD=4-2=2 BE=2-(-4)=6 CE=3-(-3)=6则S△ABC=S梯形ADEC-S△ADB-S△BEC    =1/2(5+6)×(2+6)-1/2×2×5-1/2×6...