1）在△AEB和△AEC中,AE=AE,∠AEB=∠AEC=90°,BE=CE,△AEB和△AEC全等,AB=AC,
AB=BC,AB=AC=BC,△ABC是等边三角形,AB=4,BE=1/2AB=2,AE=2√3,
菱形面积=2*S△ABC=2*1/2*4*2√3=8√3 cm2
2)菱形ABCD,△ABC和△ADC全等,是等边三角形,三条边高相等,BD=2AE=2*2√3=4√3 cm