2直角三角形直角三角形专题训练(二)直角三角形解:连接AD,AEDAFD90,AED和AFD是直角三角形,ADAD,AEAF,AEDAFD(HL),ADEADF,又ABAC,D是BC中点,ADBC,1ADE2ADF90,即12解:连接AD,ABAC,BAC120,B30,又ABAC,D为BC的中点,ADBC,AD平分BAC,BAD60,在RtABD中,B30,AB2AD,在RtADE中,EAD60,EDA30,AD2AE,即:AB4AE,AEBE4AE,BE3AE,EBEA31解:BFFCECFC,FBEC,BCEF,BE90,ABC和DEF为直角三角形,又ACDF,BCEF,ABCDEF(HL),ABDE