已知直线l和圆M:x눀+y눀+2x=0相切于点T,

2024-12-28 07:55:27
推荐回答(2个)
回答1:

A(x1,y1)
B(x2,y2)
T((x1+x2)/2,(y1+y2)/2)
M(-1,0)
x1^2-y1^2=1
x2^2-y2^2=1
(x1+x2)^2/4+(y1+y2)^2/4+(x1+x2)=0
直线AB垂直于MT,斜率之为-1
(y2-y1)/(x2-x1)*((y1+y2)/2)((x1+x2)/2+1)=-1
解得x1+x2=-3
T点坐标(-3/2,+-根号3/2)
所以MT斜率为+-根号3/3
所以AB斜率为+-根号3
l方程:
y=+-根号3x-+根号3
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回答2:

设A(x1,y1),B(x2,y2)
则:T(x3,y3)满足:2x3=x1+x2,2y3=y1+y2
x1^2-y1^2=1,x2^2-y2^2=1
(x1^2-x2^2)-(y1^2-y2^2)=0
(x1-x2)(x1+x2)=(y1-y2)(y1+y2)
Kab=(y1-y2)/(x1-x2)=(x1+x2)/(y1+y2)=x3/y3
Kto=y3/(x3+1)
因为:AB⊥OT
所以,Kab*Kto=x3/(x3+1)=-1
x3=-1/2
代人x^2+y^2+2x=0得:1/4+y3^2-1=0,y3=±√3/2
Kab=x3/y3=±√3/3

所以,直线L的方程是
y+√3/2=√3/3*(x+1/2), 即:√3y-x+1=0
或,y-√3/2=-√3/3*(x+1/2), 即:√3y+x-1=0