The value of the directional derivative of the function 𝛷(𝑥, 𝑦, 𝑧) = 𝑥𝑦2 + 𝑦𝑧2 + 𝑧𝑥2

Q. The value of the directional derivative of the function 𝛷(𝑥, 𝑦, 𝑧) = 𝑥𝑦² + 𝑦𝑧² + 𝑧𝑥² at the point (2, -1, 1) in the direction of the vector 𝐩 = 𝐢 + 2𝐣 + 2𝐤 is

(A) 1                           (B) 0.95                      (C) 0.93                      (D) 0.9

Ans: 1

Sol: