Chapter 7: Problem 90
Evaluate the integrals. \begin{equation}\int_{-2}^{0} 5^{-\theta} d \theta\end{equation}
Short Answer
Expert verified
The integral evaluates to \( \frac{24}{\ln(5)} \).
Step by step solution
01
Identify the function inside the integral
The given integral is \( \int_{-2}^{0} 5^{-\theta} \, d\theta \). This means we need to integrate the function \( 5^{-\theta} \) with respect to \( \theta \).
02
Determine the antiderivative
To integrate \( 5^{-\theta} \), we need to use the formula for integrating exponential functions. The antiderivative of \( a^{-\theta} \) with respect to \( \theta \) is \( \frac{a^{-\theta}}{-\ln(a)} + C \), as long as \( a > 0 \) and \( a eq 1 \). Here, \( a = 5 \), so the antiderivative is \( \frac{5^{-\theta}}{-\ln(5)} \).
03
Apply the limits of integration
We now evaluate the definite integral using the antiderivative: \[ \left[ \frac{5^{-\theta}}{-\ln(5)} \right]_{-2}^{0} = \frac{5^{0}}{-\ln(5)} - \frac{5^{-(-2)}}{-\ln(5)} \].
04
Simplify the expression
Calculate \( 5^{0} \) which is 1, and \( 5^{2} \) which is 25. Substitute these into the expression from Step 3: \[ \frac{1}{-\ln(5)} - \frac{25}{-\ln(5)} = \frac{1 - 25}{-\ln(5)} = \frac{-24}{-\ln(5)} = \frac{24}{\ln(5)} \]. This is the value of the integral.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Functions
Exponential functions are fundamental in mathematics, commonly denoted as \( a^x \), where \( a \) is a positive constant base and \( x \) is the exponent. They have distinct properties that make them incredibly useful, such as rapid growth or decay depending on the sign of the exponent.
Some key characteristics include:
Some key characteristics include:
- If \( a > 1 \), the function increases rapidly as \( x \) increases.
- If \( 0 < a < 1 \), the function decreases quickly as \( x \) increases.
- The graph of an exponential function has a horizontal asymptote typically at \( y=0 \).
Antiderivative
The antiderivative, or the indefinite integral, is the reverse process of differentiation. For a function \( f(x) \), the antiderivative is a function \( F(x) \) such that \( F'(x) = f(x) \). It's noted by the integral symbol with no specified limits: \( \int f(x) \, dx \).
Calculating the antiderivative:
Calculating the antiderivative:
- For exponential functions like \( a^{-\theta} \), utilize the formula \( \frac{a^{-\theta}}{-\ln(a)} + C \).
- \( C \) is the constant of integration, symbolizing that indefinite integrals can have multiple solutions.
Fundamental Theorem of Calculus
The Fundamental Theorem of Calculus bridges the concept of differentiation with integration, providing a method for evaluating definite integrals. It states that if \( F \) is an antiderivative of \( f \) over an interval \([a, b]\), then: \[ \int_{a}^{b} f(x) \, dx = F(b) - F(a) \].
Application steps include:
Application steps include:
- Find the antiderivative \( F(x) \) of \( f(x) \).
- Evaluate \( F(x) \) at both bounds \( a \) and \( b \).
- Subtract the two results: \( F(b) - F(a) \).