Find the directional derivative of f(x,y)=x2+y2f(x,y) = x^2 + y^2f(x,y)=x2+y2 at (1,1)(1,1)(1,1) in the direction u⃗=(12, 12)\vec{u} = \left(\dfrac{1}{\sqrt{2}},\; \dfrac{1}{\sqrt{2}}\right)u=(21,21).
222\sqrt{2}22
222
2\sqrt{2}2
444