Find all the second-order partial derivatives of the following function. w = 6x sin (7x°y)

Calculus: Early Transcendentals
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ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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**Problem Statement:**

**Find all the second-order partial derivatives of the following function.**

\[ w = 6x \sin \left( 7x^2y \right) \]

**Solution and Explanation:**

We are given the function \( w = 6x \sin(7x^2 y) \), and we need to find all the second-order partial derivatives. 

Define:
- \( w \) as the dependent variable.
- \( x \) and \( y \) as the independent variables.

We need to compute the four second-order partial derivatives:
1. \( \frac{\partial^2 w}{\partial x^2} \) 
2. \( \frac{\partial^2 w}{\partial y^2} \)
3. \( \frac{\partial^2 w}{\partial x \partial y} \)
4. \( \frac{\partial^2 w}{\partial y \partial x} \)

**Step-by-Step Solution:**

1. Find the first-order partial derivatives:
   - \( w_x = \frac{\partial w}{\partial x} \)
   - \( w_y = \frac{\partial w}{\partial y} \)

2. Differentiate \( w_x \) with respect to \( x \) and \( y \) to find \( w_{xx} \) and \( w_{xy} \).
3. Differentiate \( w_y \) with respect to \( x \) and \( y \) to find \( w_{yy} \) and \( w_{yx} \).

Note that due to the symmetry of mixed partial derivatives (Clairaut's theorem), \( w_{xy} \) should equal \( w_{yx} \) if the function is continuous and differentiable.

**First-Order Partial Derivatives:**

\[ w = 6x \sin(7x^2y) \]

1. **First Partial Derivative with respect to \( x \):**

\[ w_x = \frac{\partial w}{\partial x} = 6 \sin(7x^2 y) + 6x \cos(7x^2 y) \cdot \frac{\partial}{\partial x}(7x^2 y) \]
\[ w_x = 6 \sin(7x^2 y) + 6x \cos(7x^2 y) \cdot
Transcribed Image Text:**Problem Statement:** **Find all the second-order partial derivatives of the following function.** \[ w = 6x \sin \left( 7x^2y \right) \] **Solution and Explanation:** We are given the function \( w = 6x \sin(7x^2 y) \), and we need to find all the second-order partial derivatives. Define: - \( w \) as the dependent variable. - \( x \) and \( y \) as the independent variables. We need to compute the four second-order partial derivatives: 1. \( \frac{\partial^2 w}{\partial x^2} \) 2. \( \frac{\partial^2 w}{\partial y^2} \) 3. \( \frac{\partial^2 w}{\partial x \partial y} \) 4. \( \frac{\partial^2 w}{\partial y \partial x} \) **Step-by-Step Solution:** 1. Find the first-order partial derivatives: - \( w_x = \frac{\partial w}{\partial x} \) - \( w_y = \frac{\partial w}{\partial y} \) 2. Differentiate \( w_x \) with respect to \( x \) and \( y \) to find \( w_{xx} \) and \( w_{xy} \). 3. Differentiate \( w_y \) with respect to \( x \) and \( y \) to find \( w_{yy} \) and \( w_{yx} \). Note that due to the symmetry of mixed partial derivatives (Clairaut's theorem), \( w_{xy} \) should equal \( w_{yx} \) if the function is continuous and differentiable. **First-Order Partial Derivatives:** \[ w = 6x \sin(7x^2y) \] 1. **First Partial Derivative with respect to \( x \):** \[ w_x = \frac{\partial w}{\partial x} = 6 \sin(7x^2 y) + 6x \cos(7x^2 y) \cdot \frac{\partial}{\partial x}(7x^2 y) \] \[ w_x = 6 \sin(7x^2 y) + 6x \cos(7x^2 y) \cdot
The image shows partial differential equations involving a function \( w \). Here's the transcription:

\[
\frac{\partial^2 w}{\partial x^2}
\]

\[
\frac{\partial^2 w}{\partial y^2}
\]

\[
\frac{\partial^2 w}{\partial y \partial x}
\]

\[
\frac{\partial^2 w}{\partial x \partial y}
\]

### Explanation:
- **\(\frac{\partial^2 w}{\partial x^2}\)** represents the second partial derivative of \( w \) with respect to \( x \). It measures the rate at which the first derivative \(\frac{\partial w}{\partial x}\) changes as \( x \) changes.
  
- **\(\frac{\partial^2 w}{\partial y^2}\)** represents the second partial derivative of \( w \) with respect to \( y \). It measures the rate at which the first derivative \(\frac{\partial w}{\partial y}\) changes as \( y \) changes.

- **\(\frac{\partial^2 w}{\partial y \partial x}\)** and **\(\frac{\partial^2 w}{\partial x \partial y}\)** represent the mixed partial derivatives of \( w \). These measure how the function \( w \) changes as both \( x \) and \( y \) vary.

For educational context, these partial derivatives are crucial in fields such as multivariable calculus, differential equations, and mathematical physics, where they help in understanding how functions change in multiple dimensions.
Transcribed Image Text:The image shows partial differential equations involving a function \( w \). Here's the transcription: \[ \frac{\partial^2 w}{\partial x^2} \] \[ \frac{\partial^2 w}{\partial y^2} \] \[ \frac{\partial^2 w}{\partial y \partial x} \] \[ \frac{\partial^2 w}{\partial x \partial y} \] ### Explanation: - **\(\frac{\partial^2 w}{\partial x^2}\)** represents the second partial derivative of \( w \) with respect to \( x \). It measures the rate at which the first derivative \(\frac{\partial w}{\partial x}\) changes as \( x \) changes. - **\(\frac{\partial^2 w}{\partial y^2}\)** represents the second partial derivative of \( w \) with respect to \( y \). It measures the rate at which the first derivative \(\frac{\partial w}{\partial y}\) changes as \( y \) changes. - **\(\frac{\partial^2 w}{\partial y \partial x}\)** and **\(\frac{\partial^2 w}{\partial x \partial y}\)** represent the mixed partial derivatives of \( w \). These measure how the function \( w \) changes as both \( x \) and \( y \) vary. For educational context, these partial derivatives are crucial in fields such as multivariable calculus, differential equations, and mathematical physics, where they help in understanding how functions change in multiple dimensions.
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