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1归纳先导(p.25页)设圆锥面的母线与轴所成的角为θ,截面与轴所成的角为α.试观察,当θ<α<π2,0≤α<θ,α=θ时,截线分别是什么曲线?答:当θ<α<π2时,截线是椭圆;当0≤α<θ时,截线是双曲线;当α=θ时,截线是抛物线.
1 Induction Pilot (p.25) Let the angle formed by the generatrix of the conical surface and the axis be θ and the angle between the section and the axis be α. It is observed that when θ <α <π2, 0≤α <θ, α = θ, what are the curves of the stubs respectively? A: The stubs are ellipses when θ <α <π2; the hyperbolas are hyperbolic when 0≤α <θ; the diagonal is a parabola when α = θ .