1. The problem statement, all variables and given/known data Let [tex]f (x, y) = e^x^2 + 3e^y[/tex] . At the point (0, 1) find: (a) a vector u such that the directional derivative [tex]D_u f[/tex] is maximum and write down this maximum value, (b) a vector v such that [tex]D_v f = 0[/tex] 2. Relevant equations grad f / directional derivative formula 3. The attempt at a solution I can find part (a), simply calculate the gradient vector, but part (b) I don't know what to do. The answer given is: (b) Dv f is zero when v is tangent to the level curve passing through (0, 1), i.e. when v = i (or some multiple of this). I don't understand what this means.