The sign of v D ( \\ displaystyle \\ v_ ( D ) \\ , ) is a result of vector calculation .
The sign of v D ( \\ displaystyle \\ v_ ( D ) \\ , ) depends on the geometry of the optics .
The sign of v D ( \\ displaystyle \\ v_ ( D ) \\ , ) is a result of vector calculation and depends on the geometry of the optics .