以y^2=2px为ä¾å§ï¼
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对æç©çº¿ä¸ä»»æä¸åOç¹éåçä¸ç¹A(Xa,Ya),设满足é¢æçBç¹ä¸ºB(Xb,Yb),åæï¼
Ya^2=2pXaï¼ ï¼1ï¼
Yb^2=2pXbï¼ ï¼2ï¼
Ya/Xa*Yb/Xb=-1 (AOâ¥BO) ï¼3ï¼
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¥ï¼YaYb=-4p^2
ï¼1ï¼-ï¼2ï¼ï¼å¯å¾ABçæç=ï¼Yb-Ya)/(Xb-Xa)=2P/(Ya+Yb)
æ以ç´çº¿ABçæ¹ç¨ä¸º ï¼y-Ya)=2P/(Ya+Yb)*(x-Xa)
ï¼Ya+Yb)y-Ya^2-YaYb=2Px-2PXa
æ以ï¼Ya+Yb)y=2px-4p^2
å³ABçæ¹ç¨ä¸ºy=2p/(Ya+Yb)*(x-2P)
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