Chapter 4: Problem 54
Evaluate. $$ \int_{a}^{b}-e^{t} d t $$
Short Answer
Expert verified
The integral evaluates to \( e^a - e^b \).
Step by step solution
01
Identify the Structure of the Integral
The integral to evaluate is a definite integral, which means it has limits of integration (from \( a \) to \( b \)) and involves the exponential function \( -e^t \). We need to perform integration followed by substitution of the limits to solve it.
02
Integrate the Function
To find the antiderivative of \( -e^t \), we use the basic rule that the integral of \( e^t \) is \( e^t \) itself. Thus, the integral of \( -e^t \) is \(-e^t\).
03
Apply the Fundamental Theorem of Calculus
According to the Fundamental Theorem of Calculus, the value of the definite integral \( \int_{a}^{b} -e^t \, dt \) is the antiderivative evaluated at \( b \) minus the antiderivative evaluated at \( a \). Thus, the result of this integral is:\[-e^b - (-e^a) = -e^b + e^a.\]
04
Simplify the Expression
The expression \(-e^b + e^a\) is already in the simplest form. This is the result of the definite integral after applying the limits.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Function
Exponential functions, such as \( e^t \), are a fundamental part of mathematics and calculus. In an exponential function, a constant base (\( e \), the Euler's number, which is approximately 2.71828) is raised to the power of a variable. Exponential functions grow very rapidly and frequently appear in various applications including natural growth processes and compound interest calculations.
- The most common exponential function is expressed as \( e^t \), where \( e \) is the base and \( t \) is the exponent.
- These functions are characterized by their continuous and smooth curvature as well as their ability to model growth at a consistent rate.
- In this exercise, we are working with the function \( -e^t \), which is simply the negative form of the standard exponential function.
Antiderivative
An antiderivative, or the indefinite integral, is the reverse process of differentiation. It allows us to reconstruct a function from its derivative. Knowing how to find an antiderivative is essential for solving integration problems.
- For example, when you integrate a function like \( e^t \), its antiderivative is \( e^t \) itself because the derivative of \( e^t \) is \( e^t \).
- In the exercise, we are evaluating the antiderivative of \( -e^t \), which is \(-e^t\). This follows from the linearity of integration, where a constant multiplier like \(-1\) is factored out.
- Recognizing patterns in differentiation and knowing basic integration rules like this helps in handling more complex calculus problems.
Fundamental Theorem of Calculus
The Fundamental Theorem of Calculus is a critical bridge connecting differentiation and integration. It states that if a function is continuous on a closed interval, then the definite integral over that interval is connected to its antiderivative.
- Here's how it works: If you have a function \( F(t) \) that is an antiderivative of \( f(t) \), then the definite integral of \( f(t) \) from \( a \) to \( b \) is \( F(b) - F(a) \).
- In our example, given the antiderivative \(-e^t\), we evaluate \(-e^b\) and \(-e^a\), and subtract these results to obtain \(-e^b + e^a\).