1. The problem statement, all variables and given/known data Consider the function f(x,y) = cos(x^2+3y). Write down the gradient of f. Then find the lines in the x-y plabe where ∇f = 0 2. Relevant equations ∇f = (∂f/∂x,∂f/∂y) 3. The attempt at a solution -2xsin(x^2+3y) = 0 sin(x^2+3y) = 0 y = -(1/3)x^2 and -3sin(x^2+3y) = 0 sin(x^2+3y) = 0 y = -(1/3)x^2 Should I be getting the same answer? I also think I have not understood what the question is asking as the next question goes on to say find the line where ∇f is a non zero vector pointing in the y-direction. For this I have the same answer again!