Question

已知，AD与BC相交于点O,AB平行于CD求证AB:CD=OA:OD

Answer 1

因为AD与BC相交于点O,AB平行于CD
所以△AOB相似△COD
所以AB:CD=OA:OD

Answer 2

证明：∵AD与BC相交于点O ∴∠AOB=∠COD 又∵AB平行于CD ∴∠ABO=∠DCO ∴△ABO≌△COD ∴AB:CD=OA:OD

Answer 3

AB//CD，∠A=∠D，∠B=∠C△AOB∽△DOCAB/CD=AO/DO