Chapter 7: Problem 120
Find the exact area. Under \(f(x)=1 /(x+1)\) between \(x=0\) and \(x=2\)
Short Answer
Expert verified
The exact area under the curve is \( \ln 3 \).
Step by step solution
01
Understand the Problem
We need to find the area under the curve of the function \( f(x) = \frac{1}{x+1} \) from \( x=0 \) to \( x=2 \). This requires integrating the function over the given interval.
02
Set Up the Integral
To find the area under a curve represented by a function \( f(x) \) from \( x=a \) to \( x=b \), we compute the integral: \[A = \int_{a}^{b} f(x) \, dx\]For this problem, the integral is: \[A = \int_{0}^{2} \frac{1}{x+1} \, dx\]
03
Integrate the Function
The integral of \( \frac{1}{x+1} \) is given by the natural logarithm function: \[\int \frac{1}{x+1} \, dx = \ln|x+1| + C\]
04
Evaluate the Definite Integral
We now evaluate the integral from \( x = 0 \) to \( x = 2 \):\[A = \left[ \ln|x+1| \right]_{0}^{2} = \ln|2+1| - \ln|0+1|\]Simplifying, this becomes:\[A = \ln 3 - \ln 1\]
05
Simplify the Expression
Since \( \ln 1 = 0 \), the expression simplifies to:\[A = \ln 3\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Definite Integral
A definite integral is a fundamental concept in calculus, used to calculate the accumulated value of a function over a specific interval. Unlike an indefinite integral, which accounts for a family of antiderivatives, a definite integral provides a numerical value that represents the area under a curve. This area is bounded by the curve itself, the x-axis, and the vertical lines at the interval's boundaries.
When evaluating definite integrals, we follow these main steps:
When evaluating definite integrals, we follow these main steps:
- Identify the function to integrate, as well as the limits of integration.
- Find the antiderivative of the function, and then apply the Fundamental Theorem of Calculus.
- Subtract the value of the antiderivative at the lower limit from its value at the upper limit.
Area Under a Curve
Finding the area under a curve is a classic application of integral calculus. It involves using definite integrals to calculate the total area captured by a curve between given bounds on the x-axis.
The curve we consider is expressed as a function, and the area is simply the space that lies between this curve and the x-axis within a certain interval. Here’s how it works:
The curve we consider is expressed as a function, and the area is simply the space that lies between this curve and the x-axis within a certain interval. Here’s how it works:
- First, we define the function that describes the curve.
- Then, we specify the interval on the x-axis.
- We set up the definite integral with these parameters.
- Finally, we evaluate the integral, which results in the area under the curve.
Natural Logarithm Function
The natural logarithm function, denoted as \(\ln(x)\), is the inverse of the exponential function \(e^x\). It has properties that make it especially useful in integral calculus, often surfacing when integrating functions of the form \(\frac{1}{x}\) or \(\frac{1}{x + c}\).
Here are some features of the natural logarithm:
Here are some features of the natural logarithm:
- It is defined only for positive real numbers.
- Its base, \(e\), is approximately 2.71828 and is known as Euler's number.
- It simplifies calculations involving growth processes and decays.
- In integrals, \(\ln|x+1|\) arises as an antiderivative of \(\frac{1}{x+1}\), as seen in the original exercise problem.