I have wondered the problem in http://www.helsinki.fi/~hmkokko/Stuff/Esdale/index.html for over year without success. If we try to minimize the functional equation T(\theta ) = \int_0^L\frac {dx}{v_0\cos \theta(x)} in the set W = {\theta \in C^1 [0,L]|C(\theta) = y} where C(\theta) = \int_0^L\frac {v_0\sin \theta (x) + v(x)}{v_0\cos \theta (x)}dx, can the solution be represented in a closed form or not? A solution or a proof that no closed form solution exists would be nice.