3-FF_func_approx.edp

real L = 5;
real n = 20;

mesh Mesh = square(n, n, [L*x, L*y]);
plot(Mesh, wait=1); // press Enter to continue when displayed

fespace SpaceP1(Mesh, P1); // can be P0, P2, ...

SpaceP1 u = sin(x) + cos(y);
plot(u, fill=1);