Chapter 3: Problem 42
Differentiate. $$ f(x)=e^{-x^{2} / 2} $$
Short Answer
Expert verified
The derivative is \( f'(x) = -x e^{-x^2 / 2} \).
Step by step solution
01
Identify the Function Type
The given function, \( f(x) = e^{-x^2 / 2} \), is an exponential function where the exponent itself is a function of \( x \). It requires the use of the chain rule for differentiation since we have a composition of functions.
02
Apply the Chain Rule
To differentiate \( f(x) = e^{-x^2 / 2} \), use the chain rule. The chain rule states that if you have a composite function \( e^{g(x)} \), the derivative is \( e^{g(x)} \times g'(x) \). Here, \( g(x) = -x^2 / 2 \).
03
Find the Derivative of the Inner Function
Differentiate the inner function \( g(x) = -x^2 / 2 \). The derivative of \( -x^2 / 2 \) with respect to \( x \) is \( g'(x) = -x \), as the derivative of \( x^2 \) is \( 2x \) and the constant multiplier of \(-1/2\) remains.
04
Combine Results to Find the Derivative
Using the chain rule, the derivative of \( f(x) = e^{-x^2 / 2} \) is:\[f'(x) = e^{-x^2 / 2} imes (-x) = -x imes e^{-x^2 / 2}\]This combines the derivative of the inner function \( g'(x) = -x \) with the original exponential function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Function
An exponential function is a mathematical concept where the variable appears as an exponent. This is different from polynomial functions, where the variable is the base. In the exponential function \( f(x) = e^{x} \), \( e \) is the base of the natural logarithm, approximately equal to 2.718. Exponential functions are used to model growth and decay processes due to their fundamental properties that represent constant relative change.
- The function \( f(x) = e^{-x^2/2} \) is a specific type of exponential function where the exponent is itself a function of \( x \).
- This makes it crucial to approach such problems with appropriate differentiation techniques like the chain rule.
Derivative of a Function
The derivative of a function represents the rate at which the function's value changes as its input changes. It provides valuable information about the behavior of a function at any point. For a function \( f(x) \), the derivative \( f'(x) \) is a new function that gives us the slope of the tangent line to the graph of \( f \) at any point.
- Calculating derivatives is a fundamental skill in calculus that allows us to determine instantaneous rates of change and understand how functions behave.
- For example, the derivative helps in finding the velocity if the original function represents position over time.
Composite Function
A composite function is created when one function is applied to the results of another function. This scenario is common in calculus where chain rule application is necessary. If you have a function \( f(g(x)) \), \( f \) is applied to \( g(x) \), making it a composite function.
- The structure \( e^{-x^2/2} \) in the original problem is an example of a composite function.
- Here, \( g(x) = -x^2/2 \) and \( f(u) = e^{u} \), where \( u = g(x) \).