In problem 2, the Euler Lagrange equation imply that we are looking for the function y(x) such as the surface is minimal, so the solution is a cylinder, ie y(x)=constant=c=2.
In problem 2, the Euler Lagrange equation imply that we are looking for the function y(x) such as the surface is minimal, so the solution is a cylinder, ie y(x)=constant=c=2.