(1)è¿æ¥OPï¼PQ^2=OP^2-OQ^2=a^2+b^2-1, PA^2=(a-2)^2+(b-1)^2
PQ^2=PA^2, å¾a^2+b^2-1=(a-2)^2+(b-1)^2,
åç®å¾2a+b=3 å³b=3-2a â
(2) PQ^2=a^2+b^2-1,â 代å
¥ï¼PQ^2=5a^2-12a+8, å½a=6/5æ¶ï¼PQ^2çæå°å¼=4/5,
PQçæå°å¼=2â5/5
(3)设åPçåå¾ä¸ºR, å½åPä¸åOæå
Œ
±ç¹æ¶ï¼OPâ¤1+R, Râ¥OP-1=â(a^2+b^2)-1
â å¼ä»£å
¥ï¼å¾Râ¥âï¼5a^2-12a+9ï¼-1, å½a=6/5æ¶ï¼b=3/5,
Rçæå°å¼=â(9/5) -1
åP为ï¼ï¼x-(6/5))^2+(y-(3/5))^2=[â(9/5)-1]^2=(14-6â5)/5
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