0 votes 0 votes The directional derivative of $f(x,y)= \frac{xy}{\sqrt{2}} (x+y)$ at $(1,1)$ in the direction of the unit vector at an angle of $\frac{\pi}{4}$ with $y$-axis, is given by _________. Vector Analysis gate2014-ec-4 vector-analysis numerical-answers + – Milicevic3306 asked Mar 26, 2018 recategorized Feb 26, 2021 by Lakshman Bhaiya Milicevic3306 16.0k points 84 views answer comment Share Follow See all 0 reply Please log in or register to add a comment.