then H = (0,y)
OM =(x,y)
PM，HM在OM方向上的投影相等
=> PM.OM/|OM| = HM.OM/|OM|
(OM-OP).OM = (OM-OH).OM
(x-2,y).(x,y) = (x,0).(x,y)
x(x-2)+y^2 = x^2
y^2 =2x
then H = (0,y)
OM =(x,y)
PM，HM在OM方向上的投影相等
=> PM.OM/|OM| = HM.OM/|OM|
(OM-OP).OM = (OM-OH).OM
(x-2,y).(x,y) = (x,0).(x,y)
x(x-2)+y^2 = x^2
y^2 =2x