当pa与pb的斜率存在且倾斜角互补时y1+y2/y0

问题描述:

当pa与pb的斜率存在且倾斜角互补时y1+y2/y0

由题意,PA与PB斜率之和=0设PA:y-y0=k(x-x0),PB:y-y0=-k(x-x0),分别和抛物线联立则y1=2p/k -y0 ; y2=-2p/k -y0故y1+y2=-2y0,即(y1+y2)/y0=-2AB的斜率kAB=(y1-y2)/(x1-x2),由抛物线方程,x1-x2=1/2p ×(y1-y2)(y1+y2...