l

Vertical line of sum

l

Intersect with H, take the reverse extension line Ox of OH as the polar axis, and establish the polar coordinate system.

Aim the focus f.

l

Distance │HO│=p,

P(ρ, θ) is an arbitrary point on the conic section, which is connected with OP and denoted as PD ⊥ L.

, PQ⊥Ox, then OP=ρ, ∠xOP=θ.

According to the definition of conic, there are

│OP│/│PD│=e, and │PD│=│HQ│=│HO│+│OQ│=p+ρ? cosθ

therefore

ρ/(p+ρ？ Cosθ) = E. That is

ρ=ep/( 1-e？ Cosθ). Here it is.