# Right conoid

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In geometry, a right conoid is a ruled surface generated by a family of straight lines that all intersect perpendicularly to a fixed straight line, called the axis of the right conoid.

Using a Cartesian coordinate system in three-dimensional space, if we take the z-axis to be the axis of a right conoid, then the right conoid can be represented by the parametric equations:

$x=v\cos u,y=v\sin u,z=h(u)$ where h(u) is some function for representing the height of the moving line.

## Examples

A typical example of right conoids is given by the parametric equations

$x=v\cos u,y=v\sin u,z=2\sin u$ The image on the right shows how the coplanar lines generate the right conoid.

Other right conoids include:

• Helicoid: $x=v\cos u,y=v\sin u,z=cu.$ • Whitney umbrella: $x=vu,y=v,z=u^{2}.$ • Wallis’s conical edge: $x=v\cos u,y=v\sin u,z=c{\sqrt {a^{2}-b^{2}\cos ^{2}u}}.$ • Plücker’s conoid: $x=v\cos u,y=v\sin u,z=c\sin nu.$ • hyperbolic paraboloid: $x=v,y=u,z=uv$ (with x-axis and y-axis as its axes).