#tetracuspid

• Astroid — A remarkable plane curve with four sharp cusps, resembling a four-pointed star, generated by the trajectory of a fixed point on the circumference of a circle that rolls without slipping inside another fixed circle with a radius four times larger (a particular hypocycloid). Algebraically, its implicit Cartesian equation is x^(2/3) + y^(2/3) = a^(2/3), being extensively studied in analytical geometry due to its remarkable properties related to the envelope of a line segment of constant length.