Home / Get Math Help
How To Find the Directrix of a Parabola
Result
y = -a
Example plot
Example plots
Equations
x(t) = 2 a t y(t) = a t^2
y = x^2/(4 a)
r(θ) = 4 a tan(θ) sec(θ)
(for a parabola opening upward with vertex at the origin and semilatus rectum 2a)
Conic properties
{(0, a)}
p = 2 a
e = 1
L = 2 a