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âµBD=DC;EG=GC.
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åAF=FD,åAE/EG=AF/FD=1,AE=EG.
â´AE=EG=GC=(1/2)EC.
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âµBD=DC;BG=GE.
â´DGâ¥CE,DG=(1/2)EC.(ä¸è§å½¢ä¸ä½çº¿çæ§è´¨)
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åAF=DF,â AFG=â DFB.
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åBD=DC,åAG/BC=1/2.
âµAGâ¥BC.
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åCD=BD,â CDG=â BDF,åâ¿GCDââ¿FBD(ASA),DG=DF.
åDF=AF,åAF/AG=1/3.
â´AE/AC=AF/AG=1/3,å³AE=(1/3)AC=(1/2)EC.