oriented circle造句

There are exactly 204 immersing an oriented circle into the oriented plane so that it has four double points.
This is illustrated in the diagram, where the two black oriented circles are labelled with the corresponding value of the argument of the logarithm used in } } and } }.
To summarize : there is a one-to-one correspondence between points on the Lie quadric and " cycles " in the plane, where a cycle is either an oriented circle ( or straight line ) or a point in the plane ( or the point at infinity ); the points can be thought of as circles of radius zero, but they are not oriented.
It's difficult to find oriented circle in a sentence. 用oriented circle造句挺难的