Chapter 4: Problem 36
Which of the following functions are exact differentials? (a) df \(=\frac{1}{x} d x+\frac{1}{y} d y\) (b) \(d f=\frac{1}{y} d x+\frac{1}{x} d y\) (c) \(d F=2 x^{2} y^{2} d x+3 x^{3} y^{3} d y\) (d) \(d F=2 x^{2} y^{3} d x+2 x^{3} y^{2} d y\) (e) \(d F=x^{n} d x+y^{n} d y, n=\) any integer (f) \(d F=\left(x^{3} \cdot \cos y\right) d x+\left(x^{3} \cdot \sin y\right) d y\)
Short Answer
Step by step solution
Understand Exact Differentials
Analyze Option (a)
Analyze Option (b)
Analyze Option (c)
Analyze Option (d)
Analyze Option (e)
Analyze Option (f)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Partial Derivatives
- A partial derivative with respect to \( x \) considers \( y \) as constant and differentiates the function as if it only had one variable, \( x \).
- Similarly, the partial derivative with respect to \( y \) treats \( x \) as a constant.
Differential Form
- The terms \( M(x, y) \, dx \) and \( N(x, y) \, dy \) describe how a small change in the variable affects the function \( f \).
- Differential forms can describe paths through space and are foundational in fields like physics and engineering.
Condition for Exact Differential
- If this condition is met, the differential form \( df = M(x, y) \, dx + N(x, y) \, dy \) can be integrated to find the function \( f(x, y) \).
- Exact differentials are beneficial because they simplify the integration of multivariable functions.
Total Derivative
- Unlike partial derivatives, which consider one variable at a time, the total derivative takes into account simultaneous changes in all variables.
- This concept is particularly useful when modeling real-world scenarios where several factors vary together.
Mathematical Functions
- Functions can be linear or nonlinear, continuous or discontinuous, and involve polynomial, exponential, trigonometric, or other forms.
- Understanding these functions includes examining their behavior through derivatives, both partial and total.