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Consider the following functions (on the given internal, if specified). Find the inverse function, express it as a function of \(x,\) and find the derivative of the inverse function. $$f(x)=x^{2}-4, \text { for } x>0$$

Short Answer

Expert verified
Answer: The derivative of the inverse function is \(\frac{d}{dx}(\sqrt{x+4}) = \frac{1}{2\sqrt{x+4}}\).

Step by step solution

01

Swap \(x\) and \(y\) in the function

Write down the function as \(y = x^2 - 4\). Now, swap \(x\) and \(y\) and rewrite the function as \(x = y^2 - 4\).
02

Solve for \(y\) to find the inverse function

Add 4 to both sides of the equation and get \(x+4 = y^2\). Now, take the square root of both sides to solve for \(y\): $$y = \pm\sqrt{x+4}$$ Since \(x > 0,\) we only need the positive square root: $$f^{-1}(x) = \sqrt{x+4}$$
03

Find the derivative of the inverse function

To find the derivative of the inverse function, first find the derivative of the original function with respect to \(x\). Then, apply the formula for the derivative of the inverse function: The derivative of \(f(x)\) is: $$f'(x) = \frac{d}{dx}(x^2 - 4) = 2x$$ Now, apply the inverse function derivative formula: $$\frac{d}{dx}(f^{-1}(x)) = \frac{1}{f'(f^{-1}(x))}$$ Substitute the expressions for the inverse function and the derivative of the original function: $$\frac{d}{dx}(f^{-1}(x)) = \frac{1}{ 2(\sqrt{x + 4})}$$ So, the derivative of the inverse function is: $$\frac{d}{dx}(\sqrt{x+4}) = \frac{1}{2\sqrt{x+4}}$$

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Derivative of Inverse Function
Understanding the derivative of an inverse function is crucial in mathematics. When dealing with inverse functions, one can leverage the relationship between a function and its inverse to find the derivative, even for complex scenarios. To find the derivative of the inverse function, you first need the derivative of the original function \( f(x) \). Using this, you can apply a special formula that connects these derivatives.

Here's the important formula for finding the derivative of an inverse function \( f^{-1}(x) \). It is given by:
  • \( \frac{d}{dx}(f^{-1}(x)) = \frac{1}{f'(f^{-1}(x))} \)
This might look a bit complex at first glance, but it's all about substitution. You evaluate the derivative of the original function where the inverse function "operates." Essentially, this formula leverages the symmetry between a function and its inverse.

In simpler terms, you rearrange the relationship dramatically by flipping derivatives with respect to the function and its inverse. It’s a powerful mathematical concept that provides insight into the behavior of inverses and is crucial in calculus whenever you need to differentiate inverse functions.
Square Root Function
The square root function is a pivotal concept in mathematics, especially while dealing with inverse functions. It symbolizes an operation that reverses the effect of squaring a number. In many cases, especially when inversing functions, the square root operation becomes inevitable. It helps balance the squaring operation in equations.

Let’s look at a base example to understand this better. When you have an expression like \( y = x^2 - 4 \) where solving for \( y \) involves squaring, finding the inverse necessitates applying a square root to balance the equation when inversing steps.
  • For \( x = y^2 - 4 \), you solve for \( y \) using the square root: \( y = \sqrt{x+4} \)
One thing to note is that we typically consider only the positive square root for functions specified over domains like \( x > 0 \). This is because a function should ideally map a unique output for each input in order to remain well-defined as a mathematical function.

The square root function also visually transforms the graph of the quadratic in question to a domain-restricted function so that it matches the defined inputs of the inverse. It's fascinating how this transformation keeps function behavior intact while altering how we think about the input and output.
Function Inverse Formula
The formula to find the inverse of a function represents an incredibly vital tool in mathematics. To begin, understanding how this formula works is a bridge to solving inverse problems accurately. When handling functions, figures, or mathematical computations, the inverse function serves as a reversal tool for the original mappings of \( x \) and \( y \).

To find \( f^{-1}(x) \) for a given function \( f(x) \), consider these essential steps:
  • First, replace \( f(x) \) with \( y \).
  • Swap \( x \) and \( y \) to form the equation \( x = g(y) \).
  • Solve this equation for \( y \), obtaining \( y = f^{-1}(x) \).
This sequence highlights the swap mechanism and solving step, which are crucial in identifying the inverse function. In simpler terms, you rearrange the original equation while switching the dependent and independent components, followed by resolving the altered configuration. In the example provided, the inverse function of \( f(x) = x^2 - 4 \) becomes \( f^{-1}(x) = \sqrt{x+4} \).

Knowing these steps simplifies the seemingly complex inverse operations, building intuitiveness in handling mathematical inversions, paving the way for further analysis, including derivative computations.

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Most popular questions from this chapter

A store manager estimates that the demand for an energy drink decreases with increasing price according to the function \(d(p)=\frac{100}{p^{2}+1},\) which means that at price \(p\) (in dollars), \(d(p)\) units can be sold. The revenue generated at price \(p\) is \(R(p)=p \cdot d(p)\) (price multiplied by number of units). a. Find and graph the revenue function. b. Find and graph the marginal revenue \(R^{\prime}(p)\). c. From the graphs of \(R\) and \(R^{\prime}\), estimate the price that should be charged to maximize the revenue.

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