Circle Command
 Circle( <Point>, <Radius Number> )

Yields a circle with given center and radius.
 Circle( <Point>, <Segment> )

Yields a circle with given center and radius equal to the length of the given segment.
 Circle( <Point>, <Point> )

Yields a circle with given center through a given point.
 Circle( <Point>, <Point>, <Point> )

Yields a circle through the three given points (if they do not lie on the same line).
See also Compass, Circle with Center through Point, Circle with Center and Radius, and Circle through 3 Points tools. 
 Circle( <Line>, <Point> )

Creates a circle with line as axis and through the point.
 Circle( <Point>, <Radius>, <Direction> )

Creates a circle with center, radius, and axis parallel to direction, which can be a line, vector or plane.
Circle( <Point>, <Radius>, <Plane> )
yields a circle parallel to the plane and with perpendicular vector of the
plane as axis.
 Circle( <Point>, <Point>, <Direction> )

Creates a circle with center, through a point, and axis parallel to direction.
In order to avoid the ambiguity line/plane of notations in 2D and 3D, don’t use equations like 