Step 1 :Find the partial derivatives of \(f(x, y)\) with respect to \(x\) and \(y\): \(\frac{\partial f}{\partial x} = \frac{1}{y}\) and \(\frac{\partial f}{\partial y} = -\frac{x}{y^2}\)
Step 2 :The gradient of \(f\) is given by: \((\nabla f)(x, y) = \frac{1}{y} \mathbf{i} - \frac{x}{y^2} \mathbf{j}\)
Step 3 :Substitute \(x=0\) and \(y=2\) into the gradient to find the gradient of \(f\) at the point \(P=(0,2)\): \((\nabla f)(P) = \frac{1}{2} \mathbf{i}\)
Step 4 :Find the unit vector in the direction of \(\mathbf{v}=1 \mathbf{i}+1 \mathbf{j}\): \(\mathbf{u} = \frac{1}{\sqrt{2}} \mathbf{i} + \frac{1}{\sqrt{2}} \mathbf{j}\)
Step 5 :The directional derivative of \(f\) at \(P\) in the direction of \(\mathbf{v}\) is given by the dot product of the gradient of \(f\) at \(P\) and the unit vector in the direction of \(\mathbf{v}\): \(\left(D_{\mathbf{u}} f\right)(P) = \frac{1}{2\sqrt{2}}\)
Step 6 :The maximum rate of change of \(f\) at \(P\) is given by the magnitude of the gradient at \(P\): \(||(\nabla f)(P)|| = \frac{1}{2}\)
Step 7 :The direction in which the maximum rate of change occurs at \(P\) is given by the direction of the gradient at \(P\). Since the gradient at \(P\) is \(\frac{1}{2} \mathbf{i}\), the direction vector is \(\mathbf{w} = 1 \mathbf{i} + 0 \mathbf{j}\)