Physics
This problem in physics is called as Dirichlet problem for first order
PDE of Hamilton-Jacobi type (See [2])
Gaspard Monge
A geometrician
Born: 9 May 1746 in Beaune, Bourgogne, France
Died: 28 July 1818 in Paris, France
"Monge may be considered the father of differential geometry."
cited from
The MacTutor History of Mathematics
cited from
USC Vision Bibliography
The angle of intersection by two normal vectors is equivalent to that by two corresponding tangent planes and vice verse .
Seong Ik CHO