cardioide

x(t) = a (1 - cos(t)) cos(t) y(t) = a sin(t) (1 - cos(t))

(a x + x^2 + y^2)^2 = a^2 (x^2 + y^2)

r(θ) = a (1 - cos(θ))

algebraic | closed | heart | parametric | polar | quartic | roulette

A = (3 π a^2)/2

s = 8 a

d = 4

evolute | cardioid involute | cardioid