Consider the function f(x, t) = (x – ct)° + (x + ct)° where c is a constant. Calculate and dx2

Calculus: Early Transcendentals
8th Edition
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:**

Consider the function \( f(x, t) = (x - ct)^6 + (x + ct)^6 \) where \( c \) is a constant. Calculate \( \frac{\partial^2 f}{\partial x^2} \) and \( \frac{\partial^2 f}{\partial t^2} \).

---

**Calculations:**

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

   \[
   \frac{\partial^2 f}{\partial x^2} = \text{[Expression to be calculated]}
   \]

2. **Second Partial Derivative with respect to \( t \):**

   \[
   \frac{\partial^2 f}{\partial t^2} = \text{[Expression to be calculated]}
   \]

---

**Key Equations:**

- **One-dimensional wave equation:**

  \[
  \frac{\partial^2 f}{\partial x^2} = \frac{1}{c^2} \frac{\partial^2 f}{\partial t^2}
  \]

- **One-dimensional heat equation:**

  \[
  \frac{\partial f}{\partial t} = c^2 \frac{\partial^2 f}{\partial x^2}
  \]

---

**Question:**

What can be said about \( f \)?

- \( f \) satisfies the one-dimensional wave equation.
- \( f \) neither satisfies the one-dimensional wave equation nor the one-dimensional heat equation.
- \( f \) satisfies the one-dimensional heat equation.
- \( f \) satisfies both the one-dimensional wave equation and the one-dimensional heat equation.

---
Transcribed Image Text:**Problem Statement:** Consider the function \( f(x, t) = (x - ct)^6 + (x + ct)^6 \) where \( c \) is a constant. Calculate \( \frac{\partial^2 f}{\partial x^2} \) and \( \frac{\partial^2 f}{\partial t^2} \). --- **Calculations:** 1. **Second Partial Derivative with respect to \( x \):** \[ \frac{\partial^2 f}{\partial x^2} = \text{[Expression to be calculated]} \] 2. **Second Partial Derivative with respect to \( t \):** \[ \frac{\partial^2 f}{\partial t^2} = \text{[Expression to be calculated]} \] --- **Key Equations:** - **One-dimensional wave equation:** \[ \frac{\partial^2 f}{\partial x^2} = \frac{1}{c^2} \frac{\partial^2 f}{\partial t^2} \] - **One-dimensional heat equation:** \[ \frac{\partial f}{\partial t} = c^2 \frac{\partial^2 f}{\partial x^2} \] --- **Question:** What can be said about \( f \)? - \( f \) satisfies the one-dimensional wave equation. - \( f \) neither satisfies the one-dimensional wave equation nor the one-dimensional heat equation. - \( f \) satisfies the one-dimensional heat equation. - \( f \) satisfies both the one-dimensional wave equation and the one-dimensional heat equation. ---
A function \( u = f(x, y) \) with continuous second partial derivatives satisfying Laplace's equation 

\[
\frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial y^2} = 0 
\]

is called a harmonic function.

Calculate the indicated derivatives and determine if the function \( u(x, y) = x^3 - 3xy^2 \) is harmonic.

\[
\frac{\partial^2 u}{\partial x^2} = \underline{\hspace{5cm}}
\]

\[
\frac{\partial^2 u}{\partial y^2} = \underline{\hspace{5cm}}
\]

Is the function \( u = x^3 - 3xy^2 \) harmonic?

- ☐ no
- ☐ yes
Transcribed Image Text:A function \( u = f(x, y) \) with continuous second partial derivatives satisfying Laplace's equation \[ \frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial y^2} = 0 \] is called a harmonic function. Calculate the indicated derivatives and determine if the function \( u(x, y) = x^3 - 3xy^2 \) is harmonic. \[ \frac{\partial^2 u}{\partial x^2} = \underline{\hspace{5cm}} \] \[ \frac{\partial^2 u}{\partial y^2} = \underline{\hspace{5cm}} \] Is the function \( u = x^3 - 3xy^2 \) harmonic? - ☐ no - ☐ yes
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