Question

Answer 1

a: Xét ΔABE và ΔACD có

AB=AC

\(\widehat{BAE}\) chung

AE=AD

Do đó: ΔABE=ΔACD

=>\(\widehat{ABE}=\widehat{ACD}\)

b: \(\widehat{ABE}+\widehat{EBC}=\widehat{ABC}\)

\(\widehat{ACD}+\widehat{BCD}=\widehat{ACB}\)

mà \(\widehat{ABE}=\widehat{ACD};\widehat{ABC}=\widehat{ACB}\)

nên \(\widehat{EBC}=\widehat{BCD}\)

=>\(\widehat{OBC}=\widehat{OCB}\)

=>ΔOBC cân tại O

=>OB=OC

ΔAEB=ΔADC

=>BE=CD

EO+OB=EB

DO+OC=DC
mà OB=OC và EB=DC

nên OE=OD