读了文 [1 ],本人受到启发 ,现把圆的相交弦定理、切割线定理、切线长定理推广到抛物线上 .1　有关引理引理 1　设抛物线 y2 =2 px ( p 0 )的焦点为F ,过F作倾斜角为θ的直线交抛物线于A ,B两点 ,则 |AB| =2 psin2 θ.引理 2　设点P(x0 ,y0 )不在抛物线 y2=2 px( p 0 )上 ,过 I read the article [1], I was inspired, now the circular intersection chord theorem, cutting line theorem, tangent theorem extended to the parabola.1 lemma1 set the focus of the parabola y2 = 2 px (p 0) For F, F over a parabola with a tilt angle of θ at point A, B, then | AB | = 2 psin2 θ. Lemma 2 Let the point P (x0, y0) not be on the parabola y2 = 2 px (p 0 ), Too