Math Problem Statement

Calculate the gradient of p(x,y) = sqrt(16 - 3x^2 - y^2)

Solution

To calculate the gradient of the function p(x,y)=163x2y2p(x, y) = \sqrt{16 - 3x^2 - y^2}, we need to compute the partial derivatives with respect to both xx and yy.

Step 1: Partial derivative with respect to xx

The gradient of p(x,y)p(x, y) with respect to xx involves applying the chain rule.

p(x,y)=(163x2y2)1/2p(x, y) = (16 - 3x^2 - y^2)^{1/2}

The derivative of the square root function is:

ddx[(163x2y2)1/2]=12(163x2y2)1/2ddx(163x2y2)\frac{d}{dx} \left[ (16 - 3x^2 - y^2)^{1/2} \right] = \frac{1}{2} (16 - 3x^2 - y^2)^{-1/2} \cdot \frac{d}{dx}(16 - 3x^2 - y^2)

Now, take the derivative of the inside expression with respect to xx:

ddx(163x2y2)=6x\frac{d}{dx} (16 - 3x^2 - y^2) = -6x

So, the partial derivative of p(x,y)p(x, y) with respect to xx is:

px=12(163x2y2)1/2(6x)\frac{\partial p}{\partial x} = \frac{1}{2} (16 - 3x^2 - y^2)^{-1/2} \cdot (-6x)

Simplifying:

px=3x163x2y2\frac{\partial p}{\partial x} = \frac{-3x}{\sqrt{16 - 3x^2 - y^2}}

Step 2: Partial derivative with respect to yy

Now, take the partial derivative of p(x,y)p(x, y) with respect to yy, again applying the chain rule:

ddy[(163x2y2)1/2]=12(163x2y2)1/2ddy(163x2y2)\frac{d}{dy} \left[ (16 - 3x^2 - y^2)^{1/2} \right] = \frac{1}{2} (16 - 3x^2 - y^2)^{-1/2} \cdot \frac{d}{dy}(16 - 3x^2 - y^2)

Taking the derivative of the inside expression with respect to yy:

ddy(163x2y2)=2y\frac{d}{dy} (16 - 3x^2 - y^2) = -2y

So, the partial derivative of p(x,y)p(x, y) with respect to yy is:

py=12(163x2y2)1/2(2y)\frac{\partial p}{\partial y} = \frac{1}{2} (16 - 3x^2 - y^2)^{-1/2} \cdot (-2y)

Simplifying:

py=y163x2y2\frac{\partial p}{\partial y} = \frac{-y}{\sqrt{16 - 3x^2 - y^2}}

Step 3: The gradient of p(x,y)p(x, y)

The gradient of p(x,y)p(x, y), denoted as p(x,y)\nabla p(x, y), is the vector formed by the partial derivatives with respect to xx and yy:

p(x,y)=(px,py)\nabla p(x, y) = \left( \frac{\partial p}{\partial x}, \frac{\partial p}{\partial y} \right)

Substitute the expressions for the partial derivatives:

p(x,y)=(3x163x2y2,y163x2y2)\nabla p(x, y) = \left( \frac{-3x}{\sqrt{16 - 3x^2 - y^2}}, \frac{-y}{\sqrt{16 - 3x^2 - y^2}} \right)

Thus, the gradient of p(x,y)p(x, y) is:

p(x,y)=1163x2y2(3x,y)\nabla p(x, y) = \frac{-1}{\sqrt{16 - 3x^2 - y^2}} \left( 3x, y \right)

Would you like more details on the application of this result or its meaning?

Related Questions:

  1. How does the gradient of a function relate to its directional derivative?
  2. What is the physical interpretation of the gradient in this context?
  3. Can the gradient be used to find the critical points of the function?
  4. How does the gradient change for functions defined in three dimensions?
  5. How do gradients interact in multivariable optimization problems?

Tip: The gradient vector points in the direction of the steepest ascent of the function at any given point.

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Math Problem Analysis

Mathematical Concepts

Multivariable Calculus
Gradient
Partial Derivatives
Chain Rule

Formulas

Partial derivative of a function using the chain rule
Gradient formula ∇p(x, y) = (∂p/∂x, ∂p/∂y)

Theorems

Chain Rule in Calculus

Suitable Grade Level

Undergraduate Calculus (College Level)