Question

如图,已知圆O1和圆O2相交于A,B,过A作直线分别交圆O1,圆O2于C,D过B作直线分别交圆O1,圆O2于E,F

Answer 1

∠CBF=∠CEB+∠BCE=∠CAB+∠BAE=∠CAE

∠DCE=∠CAE+∠AEC=∠CBF+∠ABC=∠ABF=∠CDF

∴CE∥DF