Chapter 14: 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 of the region is 1.
Step by step solution
01
Understand the Boundaries
The region is bounded by the curve \(y = e^x\) and the lines \(y = 0\), \(x = 0\), and \(x = \ln 2\). This defines the region between the y-axis (\(x=0\)), the vertical line \(x=\ln 2\), the horizontal line \(y=0\), and the exponential curve.
02
Sketch the Region
Start by plotting the exponential curve \(y = e^x\) which increases steeply. The line \(x = 0\) is the y-axis, and \(x = \ln 2\) is a vertical line. The horizontal line \(y = 0\) is the x-axis. The region of interest is the area under \(y = e^x\) from \(x = 0\) to \(x = \ln 2\), down to the x-axis.
03
Set Up the Double Integral
The area of the region can be expressed as the iterated integral \(\int_{0}^{\ln 2} \int_{0}^{e^x} \ dy \ dx\). This integral computes the area under the curve \(y = e^x\) from \(x=0\) to \(x=\ln 2\).
04
Evaluate the Inner Integral
First, evaluate the inner integral \( \int_{0}^{e^x} dy \). This gives \( y \ Big|_{0}^{e^x} = e^x \). So the integral becomes \( \int_{0}^{\ln 2} e^x dx \).
05
Evaluate the Outer Integral
Now evaluate the outer integral \( \int_{0}^{\ln 2} e^x dx \). The antiderivative of \(e^x\) is \(e^x\), so evaluate it as \( e^x \Big|_{0}^{\ln 2} = e^{\ln 2} - e^0 \).
06
Simplify the Result
Simplify the expression \( e^{\ln 2} - e^0 \). Knowing that \(e^{\ln 2} = 2\) and \(e^0 = 1\), this results in \(2 - 1 = 1\). Thus, the area of the region is 1.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponential Function
The exponential function is a fundamental concept in calculus, known for its swiftly increasing nature. It is typically represented by the formula \(y = e^x\), where \(e\) is approximately 2.71828. This function is unique because its rate of growth is proportional to its current value, resulting in a rapid increase as \(x\) becomes larger. In the context of double integrals, the curve represented by \(y = e^x\) serves as a boundary when calculating areas bounded by other lines and curves. Understanding how the exponential graph behaves is essential for identifying and shading the correct region for integrals.
- Exponential functions increase rapidly; even small moves in \(x\) can cause large changes in \(y\).
- They intersect the y-axis at \(y=1\) when \(x=0\), which is an important point for setting up integrals.
Area Calculation
Calculating the area under a curve is a fundamental application of integral calculus. For regions bounded by irregular shapes or complex functions like exponential curves, double integrals are employed. The area beneath the curve \(y = e^x\) from \(x=0\) to \(x=\ln 2\) extends down to the x-axis. This specific boundary is typical in introductory exercises. We use a double integral because it accounts for varying values as both \(x\) and \(y\) change, effectively summing vertical "slices" through the region rather than horizontal slices as in single integrals.To compute:
- Understand the limits of integration: The limits for \(x\) are from \(0\) to \(\ln 2\).
- For each \(x\), the area is found from \(y = 0\) to \(y = e^x\).
Iterated Integrals
Iterated integrals are the building blocks of calculating areas, volumes, and other properties over a two-dimensional space. In simple terms, these involve double integrals: taking one integral and then integrating it again in a nested fashion. The order of integration can be integral to solving correctly, especially when different boundaries shape our regions of interest.In this exercise, the integral expression \(\int_{0}^{\ln 2} \int_{0}^{e^x} dy \ dx\) implies:- The inner integral \(\int_{0}^{e^x} dy\) finds the height of each slice from \(y=0\) to \(y=e^x\).- The outer integral \(\int_{0}^{\ln 2} dx\) sums these slices horizontally from \(x=0\) to \(x=\ln 2\).Through iterated integrals, we approach this layer-by-layer summation process, which is intuitive once visualized. By applying them in a methodical way, complete and accurate calculations for areas bounded by complex curves like exponential functions become achievable in calculus.