Chapter 3: Problem 48
Dive an example of: A non-polynomial function that has the tangent line approximation \(f(x) \approx 1\) near \(x=0\).
Short Answer
Expert verified
The function \( f(x) = e^{-x^2} \) satisfies the tangent approximation \( f(x) \approx 1 \) near \( x=0 \).
Step by step solution
01
Define the tangent line approximation
The tangent line approximation at a given point for a function is determined by the value of the function and its derivative at that point. For a function \( f(x) \), the tangent approximation at \( x = 0 \) is given by \( f(x) \approx f(0) + f'(0)x \). In our case, this needs to approximate \( 1 \) near \( x=0 \). Therefore, both \( f(0) = 1 \) and \( f'(0) = 0 \) must hold true.
02
Select a non-polynomial function
One simple non-polynomial function that can be considered is the exponential function \( f(x) = e^{-x^2} \). This function is not a polynomial because it involves an exponent that is not simply an integer power of \( x \).
03
Evaluate the function at x=0
We need to evaluate \( f(0) \) to check if it satisfies the first condition of the tangent line approximation. \( f(0) = e^{-0^2} = e^0 = 1 \). This meets the requirement \( f(0) = 1 \).
04
Calculate the derivative of the function
Find \( f'(x) \) for \( f(x) = e^{-x^2} \). Using the chain rule, we differentiate to get \( f'(x) = -2xe^{-x^2} \).
05
Evaluate the derivative at x=0
Calculate \( f'(0) \) to ensure \( f'(0) = 0 \). Substituting \( x = 0 \) into the derivative, \( f'(0) = -2(0)e^{-0^2} = 0 \). This satisfies the second condition of the tangent line approximation.
06
Conclusion
Having checked both conditions, \( f(0) = 1 \) and \( f'(0) = 0 \), the function \( f(x) = e^{-x^2} \) provides a tangent line approximation \( f(x) \approx 1 \) near \( x=0 \). Thus, this function satisfies the given criteria.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Non-polynomial Function
A non-polynomial function is one that cannot be expressed in the form of a polynomial, which generally consists of terms like \(a_nx^n + a_{n-1}x^{n-1} + ... + a_1x + a_0\) where \(a_n\) are constants and \(n\) is a non-negative integer. Non-polynomial functions include a wide variety of mathematical expressions such as:
- Exponential functions like \(e^x\), \(e^{-x^2}\), etc.
- Trigonometric functions such as \(\sin x, \cos x\)
- Logarithmic functions like \(\ln x\)
Exponential Function
An exponential function is characterized by its constant base raised to a variable exponent, typically in the form \(f(x) = a^{bx}\), where \(a\) is the base and \(bx\) is the exponent. A common example is \(e^x\), where \(e\) is the mathematical constant approximately equal to 2.718.Some important properties of exponential functions include:
- They grow rapidly, as the function's value gets significantly larger with small increases in \(x\).
- Their derivatives are also exponential functions, which makes them particularly important in calculus.
Derivative Calculation
The derivative of a function provides important information about its rate of change and the behavior of its graph. In this exercise, we focused on finding the derivative of the function \(f(x) = e^{-x^2}\).Using the chain rule, we calculate the derivative of a composite function like this, recognizing that the exponent contains a function of \(x\). A step-by-step breakdown is as follows:- Differentiate the outer function, which is the exponential function, yielding \(e^{-x^2}\).- Multiply the result by the derivative of the inner function, \(-x^2\), which is \(-2x\).This gives us the derivative: \[ f'(x) = -2xe^{-x^2} \]At \(x = 0\), this derivative evaluates to 0: \(f'(0) = -2(0)e^{-0^2} = 0\). This confirms the condition required for the tangent line approximation, ensuring the slope at \(x = 0\) is zero, hence, the tangent line is indeed \(f(x) \approx 1\) near \(x = 0\). Derivative calculations like this are crucial for understanding the precision and behavior of functions in various contexts.