My instructor likes to explain his topics at light speed and I could barely understand how to use Calculus of variations and the La Grange equations to solve this so I need some help please. This is the problem: Consider the functional for W = w(x,y) prescribed on partial(D), I(W) = ∫∫√1+(Wx)^2+(Wy)^2)dxdy subject to the integral constraint that J(W) = ∫∫Wdxdy = C, where C is the constant. Use a Calculus of Variations approach in conjunction with the intro of a Lagrange multiplier, λ, to show that: λ = (Wxx(1+(Wy)^2) - 2WxWyWxy + Wyy(1+(Wx)^2)) / (1+(Wx)^2+(Wy)^2)^(3/2) where Wx, Wy, Wxx, Wyy, Wxy are all partials. Now demonstrate that: λ = -2/a = -2(2∏/3C)^(1/3) Any help at all would be great. I don't even know where to start.