Example 5 Find the directional derivative of the function at the given point in the direction of the vector v.

1. f(x, y) = 1 + 2xy, P(3,4), v=

2. f(x, y, z) = *, P(4,1,1), v= y + z

Find the directional derivative of the function at the given point in the direction of the vector v. 1. f(x,y)=1+2xy,P(3,4),v=4,3 2. f(x,y,z)=y+zx,P(4,1,1),v=1,2,3