简单证明题已知：如图，AB∥DE,BC∥FE.求证：AF∥CD.
已知：如图，AB∥DE,B∥FE. 求证：AF∥CD.
OA/OE=OB/OD OC/OE=OB/OF 两式相除得OA/OC=OF/OD 所以AF∥CD