Chapter 15: Problem 5
Sketch the region bounded by the given lines and curves. Then express the region's area as an iterated double integral and evaluate the integral. The curve \(y=e^{x}\) and the lines \(y=0, x=0,\) and \(x=\ln 2\)
Short Answer
Expert verified
The area is 1.
Step by step solution
01
Sketch the Region
The curve given is an exponential function, \(y = e^x\), which crosses the y-axis at \(y=1\) and increases rapidly. The lines \(y=0\), \(x=0\), and \(x=\ln 2\) form boundaries for the region. The line \(y=0\) is the x-axis. The line \(x=0\) is the y-axis, and \(x=\ln 2\) is a vertical boundary at \(x=\ln 2\). The region of interest is below \(y = e^x\), above \(y = 0\), right of \(x = 0\), and left of \(x = \ln 2\).
02
Set Up the Double Integral
The region is vertically simple, meaning the y-boundaries are functions of x. Therefore, set up the double integral using x-integrals as outer integrals.The iterated integral is:\[\int_{x=0}^{x=\ln 2} \left( \int_{y=0}^{y=e^x} dy \right) dx\]
03
Evaluate the Inner Integral
First, evaluate the inner integral:\[\int_{y=0}^{y=e^x} dy = [y]_{0}^{e^x} = e^x - 0 = e^x\]
04
Evaluate the Outer Integral
Substitute the result from the inner integral into the outer integral:\[\int_{x=0}^{x=\ln 2} e^x \, dx\]Evaluate the integral:\[[e^x]_{0}^{\ln 2} = e^{\ln 2} - e^0 = 2 - 1 = 1\]
05
Conclusion
The area of the region bounded by the curve and lines is \(1\).
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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 mathematical expressions where a constant base is raised to a variable exponent. In our problem, the curve is represented by the exponential function \( y = e^x \). This curve illustrates a number of characteristics that make exponential functions distinctive:
- Exponential Growth: As \( x \) increases, \( e^x \) rapidly increases because the base \( e \) (approximately 2.718) is greater than 1.
- Intercept: At \( x = 0 \), \( e^0 = 1 \), meaning the curve crosses the y-axis at 1.
Definite Integrals
Definite integrals allow us to calculate the exact area under a curve over a specific interval. In this exercise, we set up a double integral to find the area of the region bounded by the curve \( y = e^x \) and lines \( y = 0 \), \( x = 0 \), and \( x = \ln 2 \). The steps involved are key to understanding how integration works:
- Inner Integral: This accounts for the area in the vertical direction, from \( y = 0 \) to \( y = e^x \), for each 'slice' or cross-section of the region.
- Outer Integral: Summed over the x-interval from \( x = 0 \) to \( x = \ln 2 \), this gathers all the slices together to compute the total area.
Area Between Curves
Finding the area between curves is a common application of calculus, often involving double integrals. In our specific problem, we are interested in the area between the curve \( y = e^x \) and the x-axis \( y = 0 \), bounded by two vertical lines \( x = 0 \) and \( x = \ln 2 \).
This area is calculated as follows:
This area is calculated as follows:
- The curve and line form a closed region, making it simple to apply double integration to find the enclosed area.
- Visually, you can view this space between the curve and x-axis as a collection of thin vertical strips, each integrated and combined to form the whole area.
- In this problem, because \( y = 0 \) forms a constant lower boundary interacting with the exponential curve, the integral simplifies neatly with the bounds for x and y clearly defined.