Chapter 7: Problem 17
For each function, find a. \(\frac{\partial w}{\partial u}\) and b. \(\frac{\partial w}{\partial v}\). $$w=(u v-1)^{3}$$
Short Answer
Expert verified
\(\frac{\partial w}{\partial u} = 3v(uv - 1)^2\); \(\frac{\partial w}{\partial v} = 3u(uv - 1)^2\).
Step by step solution
01
Identify the Function
We are given the function \(w = (uv - 1)^3\). Our task is to find the partial derivatives with respect to \(u\) and \(v\).
02
Apply the Chain Rule for \(\frac{\partial w}{\partial u}\)
To find \(\frac{\partial w}{\partial u}\), use the chain rule. Start by letting \(z = uv - 1\), so \(w = z^3\). Then, compute the two derivatives: \(\frac{\partial w}{\partial z} = 3z^2\) and \(\frac{\partial z}{\partial u} = v\). Now apply the chain rule: \(\frac{\partial w}{\partial u} = \frac{\partial w}{\partial z} \cdot \frac{\partial z}{\partial u} = 3z^2 \cdot v\). Substitute \(z = uv - 1\) to get \(3v(uv - 1)^2\).
03
Result for \(\frac{\partial w}{\partial u}\)
The partial derivative of \(w\) with respect to \(u\) is \(\frac{\partial w}{\partial u} = 3v(uv - 1)^2\).
04
Apply the Chain Rule for \(\frac{\partial w}{\partial v}\)
To find \(\frac{\partial w}{\partial v}\), follow a similar process. We have already defined \(z = uv - 1\), so \(w = z^3\). Compute \(\frac{\partial z}{\partial v} = u\). Now apply the chain rule: \(\frac{\partial w}{\partial v} = \frac{\partial w}{\partial z} \cdot \frac{\partial z}{\partial v} = 3z^2 \cdot u\). Substitute \(z = uv - 1\) to get \(3u(uv - 1)^2\).
05
Result for \(\frac{\partial w}{\partial v}\)
The partial derivative of \(w\) with respect to \(v\) is \(\frac{\partial w}{\partial v} = 3u(uv - 1)^2\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Chain Rule
The Chain Rule is a fundamental tool in calculus used to compute the derivative of a composite function. When dealing with functions such as \(w = (uv - 1)^3\), the chain rule allows us to differentiate the function with respect to one of its variables while considering the inner expressions. First, we identify \(z = uv - 1\) as our inner function, which turns our original function into an easier form, \(w = z^3\). This simplification enables us to apply standard differentiation rules comfortably.
- Differentiate the outer function: \(\frac{\partial w}{\partial z} = 3z^2\)
- Differentiate the inner function with respect to the chosen variable: \(\frac{\partial z}{\partial u} = v\) or \(\frac{\partial z}{\partial v} = u\)
Multivariable Calculus
Multivariable Calculus extends traditional calculus into functions of more than one variable. In the context of our exercise, understanding partial derivatives is crucial as it involves distinguishing how a function changes with respect to each variable independently. For the function \(w = (uv - 1)^3\), you focus on each variable one at a time.
- Partial derivative with respect to \(u\): \(\frac{\partial w}{\partial u} = 3v(uv - 1)^2\)
- Partial derivative with respect to \(v\): \(\frac{\partial w}{\partial v} = 3u(uv - 1)^2\)
Function Differentiation
Differentiating a function involves determining its rate of change. In our exercise, we find how \(w\) changes with respect to \(u\) and \(v\). Differentiation is a fundamental concept in calculus that helps us understand the underlying behavior of functions. To effectively handle function differentiation in this context:- Identify dependent and independent variables.- Use the Chain Rule when functions have nested parts, as demonstrated when we set \(z = uv - 1\).Here, differentiating \(w = (uv - 1)^3\) with respect to \(u\) involves treating \(v\) as a constant:\[\frac{\partial w}{\partial u} = 3v(uv - 1)^2\]Similarly, differentiating with respect to \(v\) while treating \(u\) as constant yields:\[\frac{\partial w}{\partial v} = 3u(uv - 1)^2\]These computations showcase how differentiation with respect to each variable isolates the specific influences each has on the function \(w\).