Question

初三平行线分线段成比例题目,急1.AB,CD,EF垂直于BD 求证1/AB+1/CD=1/EF 2.当AB CD EF由

Answer 1

1.证明：∵AB,CD,EF垂直于BD ∴AB‖CD‖EF∴∠BAD=∠FED ∠DCB=∠FEB ∠ABD=∠EFD ∠CDB=∠EFB∴△ABD∽△EFD △CDB∽△EFB∴AB/EF=BD/FD CD/EF=DB/FB移项整理,得AB=（EF×BD）/FD CD=（BD×EF）/FB则1/AB=FD/(EF×B...