Chapter 3: Problem 78
Show that if \(f(x)=x^{2},\) then the central difference quotient \(D_{0} f(c, h)\) for approximating \(f^{\prime}(c)\) is exactly equal to \(f^{\prime}(c)\)
Short Answer
Expert verified
The central difference quotient equals the derivative; both are \(2c\) for \(f(x) = x^2\).
Step by step solution
01
Define the Central Difference Quotient
The central difference quotient is defined as \(D_{0} f(c, h) = \frac{f(c+h) - f(c-h)}{2h}\). Here, \(f(x) = x^2\), so we can substitute to find \(f(c+h)\) and \(f(c-h)\).
02
Substitute into the Function
Calculate \(f(c+h)\) and \(f(c-h)\): \(f(c+h) = (c+h)^2 = c^2 + 2ch + h^2\) and \(f(c-h) = (c-h)^2 = c^2 - 2ch + h^2\).
03
Compute the Difference
Substitute the expressions for \(f(c+h)\) and \(f(c-h)\) into the central difference quotient. This gives:\[D_{0} f(c, h) = \frac{(c^2 + 2ch + h^2) - (c^2 - 2ch + h^2)}{2h}\]. Simplify the numerator to get \(4ch\).
04
Simplify the Quotient
Simplify \(D_{0} f(c, h)\) by cancelling terms:\[D_{0} f(c, h) = \frac{4ch}{2h} = 2c\].
05
Compare to the Actual Derivative
The actual derivative of \(f(x) = x^2\) with respect to \(x\) is \(f^{\prime}(x) = 2x\). At \(x = c\), \(f^{\prime}(c) = 2c\). This matches the result from the central difference quotient.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Central Difference Quotient
The central difference quotient is a crucial tool in the realm of numerical differentiation. It provides an effective way to approximate the derivative of a function at a particular point. Here's how it works:
- The formula for the central difference quotient is: \(D_{0} f(c, h) = \frac{f(c+h) - f(c-h)}{2h}\).
- This formula calculates the average rate of change using two points on either side of the given point \(c\), specifically the points \(c+h\) and \(c-h\).
- This helps in reducing error compared to other numerical methods.
Numerical Differentiation
Numerical differentiation is the process of finding an approximate derivative of a function using numerical methods. Understanding its importance requires a grasp of its application in situations where:
- The exact symbolic derivative is difficult or impossible to determine.
- The function is based on discrete data points from experiments or simulations.
Polynomial Functions
Polynomial functions, like \(f(x) = x^2\), are mathematical expressions involving powers of \(x\). These functions are among the simplest and most fundamental forms studied in calculus. They have a few key characteristics:
- Polynomial functions are continuous and differentiable everywhere across their domain.
- Simpler to differentiate since they follow straightforward rules of calculus.
- The derivative of \(f(x) = x^n\) is \(f'(x) = nx^{n-1}\).