Suppose $f(x,y)=\sqrt[\phantom{2}]{tan(x)+y}$ and $u$ is the unit vector in the direction of $0).$ Then,

$($a$)$ gradf$(x,y)=$

$($b$)$ gradf$(0\mathrm{.}2,7)=$

$($c$)f_u(0\mathrm{.}2,7)=D_{u}f(0\mathrm{.}2,7)=$