flat visor curve | kidney curve

x(t) = a (3 cos(t) - cos(3 t)) y(t) = a (3 sin(t) - sin(3 t))

(-4 a^2 + x^2 + y^2)^3 = 108 a^4 y^2

r(θ) = sqrt(2) a ((1 - cos(θ))^(1/3) + (cos(θ) + 1)^(1/3))^(3/2)

algebraic | closed | concave | parametric | roulette | sextic | simple

A = 12 π a^2

s = 24 a

d = 6

evolute | nephroid involute | nephroid