设P(x
0,y
0)是抛物线y
2=2px(p>0)上异于顶点的定点,A(x
1,y
1),B(x
2,y
2)是抛物线上的两个动点,且直线PA与PB的倾斜角互补
(1)求
的值
(2)证明直线AB的斜率是非零常数.
(I)设直线PA的斜率为kPA,直线PB的斜率为k PB由y12=2px1,y02=2px0相减得(y1-y0)(y1+y0)=2p(x1-x0)故 kPA=y1−y0x1−x0=2py1+y0(x1≠x0)同理可得 kPB=2py2+y0(x2≠x0)由PA,PB倾斜角互补知kPA=-kPB即2py1...