设B坐标是(yo^2/2p,yo),F坐标是(p/2,0),Q(-p/2,0)向量BQ=(-p/2-yo^2/2p,-yo),BF=(p/2-yo^2/2p,-yo)向量BQ*BF=0即有:(yo^2/2p)^2-p^2/4+yo^2=0yo^4/4p^2-p^2/4+yo^2=0yo^4+4p^2yo^2-p^4=0(yo^2+2p^2)^2=5p^4yo^2+2p^2=根号5p^2yo^2=(根号5-2)p^2所以,B的横坐标是x1=yo^2/(2p)=(根号5-2)p/2K(BF)=(0-yo)/(p/2-x1)=-yo/[p/2(1-根号5+2)]=-yo/[p/2(3-根号5)]故AB的方程是:y-...
|
