(选修4-1:几何证明选讲)如图,四边形ABCD内接于圆O,延长BD至点E,AD的延长线平分∠CDE.求证:AB=AC

2025-05-17 08:54:41
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回答(1):

如图,∵四边形ABCD内接于圆O,
延长BD至点E,AD的延长线平分∠CDE.
∠ABC=

1
2
∠CDE,
∠ACB=∠ADB=
1
2
∠CDE

∴∠ABC=∠ACB,
∴AB=AC.