2.焦点弦 (1)直线过抛物线y2=2px(p>0)的焦点F,与抛物线交于A(x1,y1),B(x2,y2)两点,则得焦点弦公式: 抛物线y2=2px(p>0),|AB|=p+(x1+x2); 抛物线y2=-2px(p>0),|AB|=p-(x1+x2); 抛物线x2=2py(p>0),|AB|=p+(y1+y2); 抛物线x2=-2py(p>0),|AB|=p-(y1+y2). (2)抛物线的焦点弦的常见结论: