$\"\"$

Gradient of the function :

$\"\"$ .

Directional derivative of a function :

If $\"\"$ is the unit vector, then the directional derivative of the function $\"\"$ is $\"\"$ .

$\"\"$

The function is $\"\"$ and the points are $\"\"$ .

Find the vector :

$\"\"$

Find the unit vector $\"\"$ :

$\"\"$

$\"\"$ .

Find gradient of the function :

$\"\"$

Substitute the point $\"\"$ in above equation.

$\"\"$ .

$\"\"$

Find the directional derivative.

$\"\"$

$\"\"$ .

$\"$

The directional derivative is $\"\"$ .