x(t) = a cos(t) y(t) = b sin(t)

x^2/a^2 + y^2/b^2 = 1

r(θ) = (a b)/sqrt((b^2 - a^2) cos^2(θ) + a^2)

(for an ellipse with center at the origin, semimajor axis a parallel to the x-axis, and semiminor axis b parallel to the y-axis)

algebraic | closed | conic | convex | oval | parametric | quadratic | simple

A = π a b

s = 4 a E(1 - b^2/a^2)

d = 2

{(-sqrt(a^2 - b^2), 0), (sqrt(a^2 - b^2), 0)}

L = b^2/a

p = b^2/sqrt(a^2 - b^2)

e = sqrt(1 - b^2/a^2)

piecewise | {x = -a^2/sqrt(a^2 - b^2) ∨ x = a^2/sqrt(a^2 - b^2)} | ba | (otherwise)

evolute | ellipse evolute involute | ellipse involute