设抛物线y2=8x的焦点为F,准线为l,P为抛物线上一点,PA⊥l,A为垂足.如果直线AF的斜率为,那么|PF|=(A) (B)8 (C) (D) 16解析如下:抛物线的焦点F(2,0),直线AF的方程为y=-√3(x-2),所以点A(-2,4√3)、
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![设抛物线y2=8x的焦点为F,准线为l,P为抛物线上一点,PA⊥l,A为垂足.如果直线AF的斜率为,那么|PF|=(A) (B)8 (C) (D) 16解析如下:抛物线的焦点F(2,0),直线AF的方程为y=-√3(x-2),所以点A(-2,4√3)、](/uploads/image/z/3136661-53-1.jpg?t=%E8%AE%BE%E6%8A%9B%E7%89%A9%E7%BA%BFy2%3D8x%E7%9A%84%E7%84%A6%E7%82%B9%E4%B8%BAF%2C%E5%87%86%E7%BA%BF%E4%B8%BAl%2CP%E4%B8%BA%E6%8A%9B%E7%89%A9%E7%BA%BF%E4%B8%8A%E4%B8%80%E7%82%B9%2CPA%E2%8A%A5l%2CA%E4%B8%BA%E5%9E%82%E8%B6%B3%EF%BC%8E%E5%A6%82%E6%9E%9C%E7%9B%B4%E7%BA%BFAF%E7%9A%84%E6%96%9C%E7%8E%87%E4%B8%BA%2C%E9%82%A3%E4%B9%88%7CPF%7C%3D%28A%29+%28B%298+%28C%29+%28D%29+16%E8%A7%A3%E6%9E%90%E5%A6%82%E4%B8%8B%EF%BC%9A%E6%8A%9B%E7%89%A9%E7%BA%BF%E7%9A%84%E7%84%A6%E7%82%B9F%EF%BC%882%2C0%EF%BC%89%2C%E7%9B%B4%E7%BA%BFAF%E7%9A%84%E6%96%B9%E7%A8%8B%E4%B8%BAy%3D-%E2%88%9A3%EF%BC%88x-2%EF%BC%89%2C%E6%89%80%E4%BB%A5%E7%82%B9A%EF%BC%88-2%2C4%E2%88%9A3%EF%BC%89%E3%80%81)
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