hi all
 

i have a mathematical quastion
i wana drive the weak formulation of this pde
-div( 1/sqrt(1+grad|u|^2) * grad(u) ) = 0
with u=x^2 on the boundary
could anybody help me,please?
thank you

I'm probably missing something in your question. Are you after something like using the divergence theorem to get:

integral of (<F,grad(phi)> dV) over V - integral of (phi <F,n> dS) over boundaries of V = 0, where F=grad(u)/sqrt(1+grad|u|^2) and <.,.> is an inner (dot) product, and then using the boundary conditions to get a value for the second integral?

yes but i need more simple form that include test functions to
enter in Comsol
thank you for your reply

Don't have any experience with COMSOL, so don't know what is the format that it is asking for, but in the equation that I wrote, phi was the test function.