Example: Circle
In polar coordinates, the family of circles centered about the origin is the level curves of
where is the radius of the circle. Then the orthogonal trajectories are the level curves of defined by:
The lack of complete boundary data prevents determining . However, we want our orthogonal trajectories to span every point on every circle, which means that must have a range which at least include one period of rotation. Thus, the level curves of, with freedom to choose any, are all of the curves that intersect circles, which are (all of the) straight lines passing through the origin. Note that the dot product takes nearly the familiar form since polar coordinates are orthogonal.
The absence of boundary data is a good thing, as it makes solving the PDE simple as one doesn't need to contort the solution to any boundary. In general, though, it must be ensured that all of the trajectories are found.
Read more about this topic: Orthogonal Trajectory
Famous quotes containing the word circle:
“A beauty is not suddenly in a circle. It comes with rapture. A great deal of beauty is rapture. A circle is a necessity. Otherwise you would see no one. We each have our circle.”
—Gertrude Stein (1874–1946)