Question

如图1-1-13,将长方形纸片ABCD沿着BD折叠,使点C落在C`处,BC`交AD于E,若AD=8,AB=4,求S△BE

Answer 1

设DE=X,AE=8-X.易证,BE=DE,在直角三角形ABE中,AB=4,BE=X,AE=8-X由勾股定理解得,X=5,所以,S△BED=5*4/2=10