Cho đường tròn tâm O và A thuộc (O) trên OA lấy B sao cho OB =⅓ OA vẽ đường tròn đường kính AB

a,Vẽ đường tròn đồng tâm (O) với đường tròn (O) cắt đường tròn đường kính AB tại C. Tia ac cắt 2 đường tròn đồng tâm tại C và E.D nằm giữa C và E. Chứng minh: AC=CD=DE

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