Definition:Double Cusp

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Definition

A double cusp is a cusp in which $2$ or more parts of the curve are both continuous through the point.

That is, the curve is tangential to itself.


Double Cusp of the First Kind

A double cusp of the first kind is a double cusp in which both parts of the curve lie on opposite sides of the coincident tangents defining that double cusp.

Double-cusp-first-kind.png


Double Cusp of the Second Kind

A double cusp of the second kind is a double cusp in which both parts of the curve lie on the same side of the coincident tangents defining that double cusp.

Double-cusp-second-kind.png


Point of Osculoinflection

A point of osculoinflection is a double cusp in which one or both parts of the curve has a point of inflection at the point of contact with the tangents defining that double cusp.

Osculoinflection.png


Also known as

A double cusp is also known as a tacnode or an osculation.


Also see

  • Results about double cusps can be found here.


Sources