ç´çº¿çæ¹ååé为 a=ï¼1ï¼â3ï¼ï¼
设 P ï¼xï¼yï¼æ¯ç´çº¿ä¸ä»»ä¸ç¹ï¼ä¸ AP=t*a ï¼
å x-1=t ï¼y-2=â3*t ï¼
å³ x=t+1 ï¼y=â3*t+2 ãè¿å°±æ¯ç´çº¿çåæ°æ¹ç¨ã
代å
¥å¯å¾ (t+1)^2+(â3t+2)^2=9 ï¼
åç®å¾ 4t^2+(4â3+2)t-4=0 ï¼
ææ±çè·ç¦»ä¹ç§¯ä¸º |t1|*|t2|=|t1*t2|=|-4/4|=1 ã
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