Find the directional derivative of v^(2) at the point (2 0 3) in the d...
Step 1: Understanding the Directional Derivative
The directional derivative of a function at a point in a specified direction indicates how the function changes as you move in that direction. It is calculated using the gradient of the function and the unit vector of the direction.
Step 2: Given Function and Point
- The function v = xy^2 + zy^2 + xz^2.
- Evaluate at the point (2, 0, 3).
Step 3: Calculating the Gradient
- The gradient (∇v) is derived by taking partial derivatives:
- ∂v/∂x = y^2 + z^2
- ∂v/∂y = 2xy + 2zy
- ∂v/∂z = y^2 + 2xz
- At the point (2, 0, 3):
- ∇v(2, 0, 3) = (0 + 3^2, 2(2)(0) + 2(3)(0), 0 + 2(2)(3)) = (9, 0, 12).
Step 4: Finding the Outer Normal of the Sphere
- The sphere equation is x^2 + y^2 + z^2 = 14.
- The gradient of the sphere function gives the normal vector:
- ∇g = (2x, 2y, 2z).
- At the point (3, 2, 1):
- ∇g(3, 2, 1) = (6, 4, 2).
Step 5: Normalizing the Normal Vector
- Calculate the magnitude of ∇g:
- ||∇g|| = √(6^2 + 4^2 + 2^2) = √(56) = 2√14.
- The unit normal vector (n):
- n = (6/2√14, 4/2√14, 2/2√14) = (3/√14, 2/√14, 1/√14).
Step 6: Calculating the Directional Derivative
- The directional derivative D_n v at (2, 0, 3) in the direction of n:
- D_n v = ∇v · n.
- Calculate:
- D_n v = (9, 0, 12) · (3/√14, 2/√14, 1/√14) = (27/√14 + 0 + 12/√14) = 39/√14.
Final Result
The directional derivative of v at (2, 0, 3) in the direction of the outer normal of the sphere at (3, 2, 1) is 39/√14.