Chapter 11: Problem 4
In Exercises \(1-8,\) find the Taylor polynomials of orders \(0,1,2,\) and 3 generated by \(f\) at \(a .\) $$ f(x)=1 /(x+2), \quad a=0 $$
Short Answer
Expert verified
The Taylor polynomials are \( \frac{1}{2} \), \( \frac{1}{2} - \frac{1}{4}x \), \( \frac{1}{2} - \frac{1}{4}x + \frac{1}{8}x^2 \), and \( \frac{1}{2} - \frac{1}{4}x + \frac{1}{8}x^2 - \frac{1}{16}x^3 \).
Step by step solution
01
Understand the Taylor Polynomial Formula
The Taylor polynomial of order \( n \) for a function \( f(x) \) about \( a \) is given by:\[ T_n(x) = f(a) + f'(a)(x-a) + \frac{f''(a)}{2!}(x-a)^2 + \cdots + \frac{f^{(n)}(a)}{n!}(x-a)^n \]where \( f^{(k)}(a) \) is the \( k \)-th derivative of \( f(x) \) evaluated at \( x = a \).
02
Calculate the Function and Its Derivatives at a=0
Calculate the function and its derivatives at \( x = 0 \):- \( f(x) = \frac{1}{x+2}, \) so \( f(0) = \frac{1}{2} \).- Derivative: \( f'(x) = -\frac{1}{(x+2)^2}, \) so \( f'(0) = -\frac{1}{4} \).- Second derivative: \( f''(x) = \frac{2}{(x+2)^3}, \) so \( f''(0) = \frac{1}{4} \).- Third derivative: \( f'''(x) = -\frac{6}{(x+2)^4}, \) so \( f'''(0) = -\frac{3}{4} \).
03
Construct the Taylor Polynomial of Order 0
The Taylor polynomial of order 0 is simply the function evaluated at \( a \):\[ T_0(x) = f(0) = \frac{1}{2} \]
04
Construct the Taylor Polynomial of Order 1
Add the first derivative term to the constant term:\[ T_1(x) = \frac{1}{2} - \frac{1}{4}(x-0) = \frac{1}{2} - \frac{1}{4}x \]
05
Construct the Taylor Polynomial of Order 2
Include up to the second derivative:\[ T_2(x) = \frac{1}{2} - \frac{1}{4}x + \frac{1}{8}x^2 \]The \( \frac{1}{8} \) term comes from \( \frac{1}{2!} \cdot \frac{1}{4} \).
06
Construct the Taylor Polynomial of Order 3
Include up to the third derivative:\[ T_3(x) = \frac{1}{2} - \frac{1}{4}x + \frac{1}{8}x^2 - \frac{1}{16}x^3 \]The \( \frac{1}{16} \) term comes from \( \frac{1}{3!} \cdot \left(-\frac{3}{4}\right) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Derivatives
In calculus, a derivative is a measure of how a function changes as its input changes. Derivatives tell us the rate at which a function is changing. This can be particularly useful in understanding dynamic systems in physics or economics.When you calculate the derivative at a given point, you are essentially finding the slope of the tangent line to the function's graph at that point. For a function like \( f(x) = \frac{1}{x+2} \), we can compute derivatives step-by-step:
- First Derivative \( f'(x) \): Computes the slope of the function's graph, which gives us \( f'(x) = -\frac{1}{(x+2)^2} \). It indicates how quickly \( f(x) \) decreases as \( x \) increases.
- Second Derivative \( f''(x) \): Measures the rate of change of the first derivative, calculated as \( f''(x) = \frac{2}{(x+2)^3} \). It's related to the concavity of the function—a positive second derivative suggests the graph is concave up.
- Third Derivative \( f'''(x) \): Measures the rate of change of the second derivative, given by \( f'''(x) = -\frac{6}{(x+2)^4} \).
Polynomial Approximation
Polynomial approximation helps us understand functions by representing them as simpler polynomial equations. This is especially useful when the exact form of a function is too complex to work with easily.A Taylor polynomial approximates a function using information about its derivatives at a specific point. Here’s the breakdown for the Taylor series used in the exercise:
- Order 0 Polynomial \( T_0(x) \): This is the simplest approximation, which is just the function's value at \(a = 0\), calculated as \( T_0(x) = \frac{1}{2} \).
- Order 1 Polynomial \( T_1(x) \): Incorporates the function's first derivative, giving a linear approximation: \( T_1(x) = \frac{1}{2} - \frac{1}{4}x \).
- Order 2 Polynomial \( T_2(x) \): Includes the second derivative, leading to a quadratic approximation: \( T_2(x) = \frac{1}{2} - \frac{1}{4}x + \frac{1}{8}x^2 \).
- Order 3 Polynomial \( T_3(x) \): Adds the third derivative, resulting in a cubic approximation: \( T_3(x) = \frac{1}{2} - \frac{1}{4}x + \frac{1}{8}x^2 - \frac{1}{16}x^3 \).
Function Evaluation
In mathematical analysis, function evaluation involves calculating the result of a function at specific values of its variables. This process allows us to understand the behavior and characteristics of functions better.While solving the exercise, function evaluation plays a crucial role:
- Evaluating \( f(x) \) at \( a = 0 \): First, we compute \( f(0) = \frac{1}{2} \), which is the value of the function at the center of our Taylor expansion.
- Evaluating Derivatives at \( a = 0 \): We also calculate the first, second, and third derivatives at this point: \( f'(0) = -\frac{1}{4} \), \( f''(0) = \frac{1}{4} \), \( f'''(0) = -\frac{3}{4} \). These values are crucial for constructing the Taylor polynomials.