解题方法
1 . 抛物线有如下光学性质:由其焦点射出的光线经抛物线反射后,沿平行于抛物线对称轴的方向射出,反之,平行于抛物线对称轴的入射光线经抛物线反射后反射光线或其反向延长线必过抛物线的焦点.已知抛物线
,O为坐标原点.一束平行于x轴的光线
从点
射入,经过C上的点
反射后,再经C上另一点
反射后,沿直线
射出,经过点
.
(1)求证:
;
(2)若PB平分
,求点B到直线QP的距离.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6fa2c731aaa4005382d5b4324e29fbb0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2e9b0f5f44abbc6544a2f672b025b013.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/366fdb81704c6dfee621423617176e0f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/12a3efb79f35db8448f3391252ab7d4e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8df332f01628130c084fd46aaca0a4b7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3f6f17bc385bafb37e8f964e5eb99cd0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ed2bbf5853f9565d4e5814c71dbab1a4.png)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/77d681a7a9830fe11598654e141aa28e.png)
(2)若PB平分
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/95108f5aa7f7ed0f6e556fb50cdbae98.png)
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