Find the directional derivative of f(x,y)=ln(x2+y2)f(x, y) = \ln(x^2+y^2)f(x,y)=ln(x2+y2) at (1,1)(1, 1)(1,1) in the direction of the vector ⟨1,1⟩\langle 1, 1 \rangle⟨1,1⟩.
111
2\sqrt{2}2
1/21/\sqrt{2}1/2
000