Solution: The gradient of the scalar function V ¼ xy2 + y2z is first calculated. This gives the directional derivative in the normal direction. Then, we evaluate the gradient at point P (1,1,1) and find the projection of this vector onto the vector A ¼ ^ x3þ ^ y4 using the scalar product between the gradient and the unit vector ^ A. This gives the magnitude (or scalar component) of the directional derivative and is the derivative in the required direction. The scalar function is