Math Problem Statement
Find the directional derivative of f(x,y,z)=z3−x2y at the point (-2, 5, 2) in the direction of the vector v=⟨−3,−1,2⟩.
Solution
To find the directional derivative of the function at the point in the direction of the vector , follow these steps:
Step 1: Find the gradient of the function
The gradient of , denoted by , is the vector of partial derivatives:
- Partial derivative with respect to :
- Partial derivative with respect to :
- Partial derivative with respect to :
Thus, the gradient is:
Step 2: Evaluate the gradient at the point
Substitute , , and into the gradient:
Step 3: Normalize the direction vector
The direction vector needs to be normalized:
The normalized vector is:
Step 4: Compute the directional derivative
The directional derivative of at the point in the direction of is given by the dot product of the gradient and the normalized vector:
Thus, the directional derivative is:
Would you like more details on any part of this solution?
Here are 5 related questions:
- How do you interpret the magnitude of the directional derivative?
- What does it mean if the directional derivative is positive or negative?
- How would the directional derivative change if the direction vector were different?
- Can you find the maximum rate of change of the function at a given point?
- How do gradient vectors relate to level curves or surfaces?
Tip: The magnitude of the gradient indicates the steepest ascent direction and rate of change at a point.
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Math Problem Analysis
Mathematical Concepts
Directional Derivatives
Gradient Vectors
Multivariable Calculus
Vector Normalization
Dot Product
Formulas
Gradient of f: ∇f(x, y, z) = (∂f/∂x, ∂f/∂y, ∂f/∂z)
Directional derivative: D_𝑣 f = ∇f ⋅ u
Vector normalization: u = v / |v|
Dot product: A ⋅ B = A₁B₁ + A₂B₂ + A₃B₃
Theorems
Gradient Theorem
Properties of Dot Product
Suitable Grade Level
Grades 11-12 or Early College
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