[中學] 圓與直線
http://i.imgur.com/eH2jH8o.jpg?2
一中段考題。
手頭沒答案,這樣算答案有對嗎?怕算錯。
或是有啥更好算法?
x^2 + y^2 + 3x + 2y + 3 = 0
設P為(m,n),Q(x,y)
(m-3)^2 + (n-2)^2 =1
√(m^2 + n^2)√(x^2 + y^2) =6
設t= m/x = n/y ,t<0
√((xt)^2 + (yt)^2)√(x^2 + y^2) = (x^2 + y^2)|t|
= -(x^2 + y^2)t=6 => t = -6/(x^2 + y^2)
(xt-3)^2 + (yt-2)^2 =1
(x^2 + y^2)t^2 -(6x+4y)t + 12 =0
=>x^2 + y^2 + 3x + 2y + 3 = 0
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迷途中唯一的導航 是對自己誠實
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※ 編輯: Tiderus (123.240.91.95), 11/22/2015 23:50:38
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