Chapter 6: Problem 91
Are the statements is true or false? Give an explanation for your answer. An antiderivative of \(e^{-x^{2}}\) is \(-e^{-x^{2}} / 2 x\)
Short Answer
Expert verified
False; the derivative of \(-e^{-x^{2}} / 2x\) is not \(e^{-x^{2}}\).
Step by step solution
01
Understand the Statement
The statement is asking whether \(-e^{-x^{2}} / 2x\) is an antiderivative of \(e^{-x^{2}}\). This means we need to check if the derivative of \(-e^{-x^{2}} / 2x\) is \(e^{-x^{2}}\).
02
Differentiate the Given Function
To determine if \(-e^{-x^{2}} / 2x\) is an antiderivative, calculate its derivative. Use the quotient rule: If \(f(x) = \frac{u(x)}{v(x)}\), then \[ f'(x) = \frac{u'(x)v(x) - u(x)v'(x)}{(v(x))^2} \].In this case, \(u(x) = -e^{-x^{2}}\) and \(v(x) = 2x\).
03
Apply the Quotient Rule
Find \(u'(x)\) and \(v'(x)\):- \(u'(x) = \frac{d}{dx}[-e^{-x^{2}}] = 2xe^{-x^{2}}\) (using the chain rule),- \(v'(x) = \frac{d}{dx}[2x] = 2\).Substitute these into the quotient rule formula: \[ f'(x) = \frac{2xe^{-x^{2}}(2x) - (-e^{-x^{2}})(2)}{(2x)^2} = \frac{4x^2e^{-x^{2}} + 2e^{-x^{2}}}{4x^2}\].
04
Simplify the Expression
Simplify the expression for \(f'(x)\):\[ f'(x) = \frac{4x^2e^{-x^{2}} + 2e^{-x^{2}}}{4x^2} = \frac{2e^{-x^{2}}(2x^2 + 1)}{4x^2} = \frac{e^{-x^{2}} (2x^2 + 1)}{2x^2}\].The result is not \(e^{-x^{2}}\), which would be necessary for the original statement to be true.
05
Conclusion
The derivative of \(-e^{-x^{2}} / 2x\) is not \(e^{-x^{2}}\). Therefore, the statement that \(-e^{-x^{2}} / 2x\) is an antiderivative of \(e^{-x^{2}}\) is false.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Chain Rule
The chain rule is a fundamental concept in calculus that is used to find the derivative of composite functions. A composite function is one where a function is applied inside another function, like \(e^{-x^2}\). To use the chain rule effectively, you identify the outer function and the inner function.
In the expression \(e^{-x^2}\), the outer function is the exponential function \(e^u\), where \(u = -x^2\), and the inner function is \(-x^2\). The chain rule states that the derivative of a composite function \(f(g(x))\) is given by the formula \[f'(g(x)) \, \cdot \, g'(x)\].
In the expression \(e^{-x^2}\), the outer function is the exponential function \(e^u\), where \(u = -x^2\), and the inner function is \(-x^2\). The chain rule states that the derivative of a composite function \(f(g(x))\) is given by the formula \[f'(g(x)) \, \cdot \, g'(x)\].
- Determine \(f(u)\). Here, \(f(u) = e^u\). The derivative is \(f'(u) = e^u\).
- Determine \(g(x)\). For this, \(g(x) = -x^2\). Its derivative is \(g'(x) = -2x\).
- Apply the chain rule: the derivative of \(e^{-x^2}\) is \((-2x) \, \cdot \, e^{-x^2}\).
Utilizing the Quotient Rule
The quotient rule is another essential tool in differentiation, especially useful when dealing with division of two functions. If you have a function \(f(x) = \frac{u(x)}{v(x)}\), the derivative is given by \[ f'(x) = \frac{u'(x)v(x) - u(x)v'(x)}{(v(x))^2} \].
When considering the problem's function \(-\frac{e^{-x^2}}{2x}\), employ the quotient rule.
When considering the problem's function \(-\frac{e^{-x^2}}{2x}\), employ the quotient rule.
- Identify \(u(x) = -e^{-x^2}\) and \(v(x) = 2x\).
- Find the derivatives \(u'(x) = 2xe^{-x^2}\) (using the chain rule) and \(v'(x) = 2\).
- Substitute into the quotient rule formula: \[\frac{2xe^{-x^2} \cdot 2x + e^{-x^2} \cdot 2}{4x^2} = \frac{4x^2e^{-x^2} + 2e^{-x^2}}{4x^2} \].
The Process of Differentiation
Differentiation is the method of finding how a function changes as its input changes. It is a foundational concept in calculus that deals with calculating the derivative of a function. A derivative represents the rate of change or slope of the function at any given point.
In calculus, when you differentiate a function, you determine its behavior and how it reacts to changes. This is particularly significant in finding how a composite or a quotient function behaves, which requires techniques like the chain rule or quotient rule.
In calculus, when you differentiate a function, you determine its behavior and how it reacts to changes. This is particularly significant in finding how a composite or a quotient function behaves, which requires techniques like the chain rule or quotient rule.
- The derivative expresses how function outputs vary with small changes in inputs, giving insights into rates of change.
- It is vital in solving practical problems involving motion, growth rates, and optimizations.
- In examining if a function \(-\frac{e^{-x^2}}{2x}\) is an antiderivative, you calculate its derivative to determine if it matches \(e^{-x^2}\).