【求助】圆锥曲线-双曲线相关题,百度不到.

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【求助】圆锥曲线-双曲线相关题,百度不到.

【求助】圆锥曲线-双曲线相关题,百度不到.
【求助】圆锥曲线-双曲线相关题,

百度不到.

【求助】圆锥曲线-双曲线相关题,百度不到.
(1)
设双曲线为x²/a² - y²/b² = 1
c = 2
a² + b² = c² = 4,b² = 4 - a²
x²/a² - y²/(4 - a²) = 1 (i)
切线:y - 0 = 2(x - 1/2),y = 2x - 1
代入(i)整理得:(4 - 5a²)x² + 4a²x + a²(a² - 5) = 0 (ii)
判别式∆ = (4a²)² - 4(4 - 5a²)a²(a² - 5) = 20a²(a⁴ - 5a² + 4) = 20a²(a² - 1)(a² - 4) = 0
a² = 1 (舍去a² = 0,a² = 4)
b² = 4 - 1 = 3
x² - y²/3 = 1
(2)
(ii)变为x² - 4x + 4 = (x - 2)² = 0
x = 2
P(2,3)
PF₁的方程:(y - 0)/(3 - 0) = (x + 2)/(2 + 2),3x - 4y + 6 = 0
PF₂的方程:x= 2,x - 2 = 0
Q与PF₁的距离d₁ = |3/2 -0 + 6|/√(3² + 4²) = 3/2
Q与PF₂的距离d₂ = 2 - 1/2 = 3/2
d₁ = d₂
PQ为角F₁PF₂的平分线