已知椭圆x^2/2+y^2=1,求斜率为2的平行线的中点的轨迹方程
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2013-12-06
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中点P(x,y)
(yA-yB)/(xA-xB)=2
xA+xB=2x,yA+yB=2y
x^2/2+y^2=1
x^2+2y^2=2
(xA)^2+2(yA)^2=2......(1)
(xB)^2+2(yB)^2=2......(2)
(1)-(2):
(xA+xB)*(xA-xB)+2(yA+yB)*(yA-yB)=0
(xA+xB)+2(yA+yB)*(yA-yB)/(xA-xB)=0
2x+2*2y*2=0
弦中点的轨迹方程:x+4y=0
(yA-yB)/(xA-xB)=2
xA+xB=2x,yA+yB=2y
x^2/2+y^2=1
x^2+2y^2=2
(xA)^2+2(yA)^2=2......(1)
(xB)^2+2(yB)^2=2......(2)
(1)-(2):
(xA+xB)*(xA-xB)+2(yA+yB)*(yA-yB)=0
(xA+xB)+2(yA+yB)*(yA-yB)/(xA-xB)=0
2x+2*2y*2=0
弦中点的轨迹方程:x+4y=0
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