- a curve having a cusp at the origin and a point of inflection at infinity. Equation: r = 2a sin(θ)tan(θ).
- a geometric curve whose two branches meet in a cusp at the origin and are asymptotic to a line parallel to the y -axis. Its equation is y ²(2a – x) =x ³ where 2a is the distance between the y -axis and this line
- contained between the concave sides of two intersecting curves
