The quadratic function  is well known in mathematics and has many applications in the real world, especially, in physics. Stenlund [2] proved that if  is quadratic, then the locus of intersection points of any two tangent lines is congruent to the graph of the original function  with a vertical shift if the two points are horizontally equispaced. Krasopoulos [1] generalized this result to n-dimensional space  However, both Stenlund and Krasopoulos did not address the converse. In this paper, we prove the converse.

characterization, quadratic function, tangent plane.