Level Set

The level set of a differentiable function  corresponding to a real value  is the set of points

For example, the level set of the function  corresponding to the value  is the sphere  with center  and radius .

If , the level set is a plane curve known as a level curve. If , the level set is a surface known as a level surface.

REFERENCES:

Gray, A. "Level Surfaces in ." §12.7 in Modern Differential Geometry of Curves and Surfaces with Mathematica, 2nd ed. Boca Raton, FL: CRC Press, pp. 291-293, 1997.