Question: Given \(f\left( x,y \right)=\ln \sqrt{{{x}^{2}}+{{y}^{2}}}\), find

(a) The direction and maximum rate of increase of \(f\left( x,y \right)\) at (1, 2).

(b) The directional derivative of \(f\left( x,y \right)\) at (1, 2) in the direction of the vector (-4, 3)