Question

初二数学+过程

Answer 1

• (1)因为在△abc中，d、e、f分别是bc、ac、ab、上的中点                                                      所以 fe 平行且等于bc，ed平行且等于ab （  三角形的中位线定理）                                       所以四边形bdef是平行四边形                                                                                                   又因为 ab等于bc                                                                                                                       所以fe=ed                                                                                                                                    所以四边形bdef是菱形                                                                                                                                                                                                                                                                                                                                                                   （2) 因为四边形bdef是菱形                                                                                               所以fb=bd=de=ef                                                                                                                      又因为f为ab上的中点                                                                                                                所以bf=1/2ab=1/2×12=6(cm)                                                                                                    菱形bdef的周长为4×6=24cm