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91Ó°ÊÓ

Use any method (including geometry) to find the area of the following regions. In each case, sketch the bounding curves and the region in question. The region in the first quadrant bounded by \(y=2\) and \(y=2 \sin x\) on the interval \([0, \pi / 2]\)

Short Answer

Expert verified
Answer: The area of the region is π square units.

Step by step solution

01

Sketch the Bounding Curves and the Region

First, let's sketch the given functions and the region. We know that y=2 is a horizontal line passing through point (0,2), and y=2sin(x) is a sine function with the amplitude of 2. Since both functions are positive for \(x\in [0, \pi / 2]\), the bounded region will lie entirely in the first quadrant. Sketch the graph of each function and shade the region between them. You will see that y=2sin(x) has a maximum value of 2 at x=Ï€/2, which is where it intersects with y=2.
02

Setup the Integration

Now we need to evaluate the integral representing the area of the region. The area can be found by finding the difference between the two functions (y=2 and y=2sin(x)) and integrating that difference over the given interval (\([0, \pi / 2]\)): \(A = \int_{0}^{\pi/2} (2 - 2\sin x) dx\)
03

Evaluate the Integral

Now, we'll evaluate the integral: \(A = \int_{0}^{\pi/2} (2 - 2\sin x) dx = 2\int_{0}^{\pi/2}(1-\sin x) dx\) Using the antiderivative rules, we will integrate each term separately: \(2\left(\int_{0}^{\pi/2} 1 dx - \int_{0}^{\pi/2} \sin x dx\right)\) The antiderivative of 1 is x, and the antiderivative of sin(x) is -cos(x): \(2\left(\left[x\right]_{0}^{\pi/2} - \left[-\cos x\right]_{0}^{\pi/2}\right)\)
04

Evaluate the Limits and Find the Area

Finally, we will evaluate the limits: \(2\left(\left[\frac{\pi}{2} - 0\right] - \left[-1 - (-1)\right]\right)\) Simplify the expression: \(2\left(\frac{\pi}{2} - 0\right) = \pi\) The area of the given region is \(\pi\) square units.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Definite Integrals
Definite integrals are fundamental in calculus for measuring the total accumulation of quantities, such as area under a curve or the total distance traveled. They offer a way to calculate areas by considering the entire region between curves over an interval. In our problem, we used a definite integral to find the area between two functions: a constant function, \(y = 2\), and a trigonometric function, \(y = 2\sin(x)\), over a specified range from \(x = 0\) to \(x = \pi/2\).
The process involves setting up an integral with these bounding curves, subtracting the lower function from the upper function, and integrating over the given interval. This gives us:
  • \(A = \int_{0}^{\pi/2} (2 - 2\sin x) dx\)
Here, the definite integral calculates the exact area encapsulated between these two curves across the interval, capturing how one function rises over and dips below another. Understanding this concept is crucial for accurately evaluating areas in various practical contexts, such as physics and engineering.
By calculating definite integrals, we can also determine other quantifiable physical properties, as they provide a foundation for integral calculus.
Area under Curves
Finding the area under curves is a common application of calculus, especially with definite integrals. In our task, we determined the region enclosed between \(y = 2\) and \(y = 2\sin(x)\). By calculating the integral, we identified the enclosed area across the interval \([0, \pi/2]\). This interval corresponds to one quadrant where the functions intersect.
To calculate this area, we examined the behavior of these curves graphically. The curve \(y = 2\sin(x)\) traces a wave pattern that peaks at \(x = \pi/2\), exactly reaching \(y = 2\). The area of interest lies between \(y = 2\) and this curve, adjusting to the specific characteristics of \(2\sin(x)\).
Visualizing this setup helps define which part of the graph contributes to the area. We considered where the curves met, noting that at \(x = \pi/2\), they intersect, marking the endpoint of integration.
  • The difference in function values reflects the height at each interval, providing insight into constructing the integral as \(\int_{0}^{\pi/2} (2 - 2\sin x) \; dx\).
This practical approach helps to clarify the concept of area as the net accumulation of small rectangle areas summed up, underlining the integral calculus's role in precise area calculation.
Trigonometric Functions
Trigonometric functions often appear in calculus due to their periodic nature, providing unique interaction with graphical analysis. In our exercise, we focused on \(y = 2\sin(x)\), a variation of the basic sine function scaled by 2. This scaling impacts the amplitude, altering how high or low the curve reaches on a graph.
The sine function itself is defined by its periodic oscillations, repeating every \(2\pi\), but here we restrict it to the interval \([0, \pi/2]\). Within this window, \(2\sin(x)\) rises from zero to its maximum value at \(x = \pi/2\), where it equals \(2\).
  • Understanding \(2\sin(x)\) includes knowledge of trigonometric identities and properties like symmetry, which are essential to manage more complex calculus problems involving waves or rotations.
Sine curves are crucial in various applications such as signal processing, physics, and engineering, given their ability to depict alternative wave forms. This example shows how trigonometric curves intersect with linear functions, specifying boundaries crucial for calculating areas and more advanced analyses like Fourier series and modeling cyclical phenomena.

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Most popular questions from this chapter

Find the area of the region bounded by the curve \(x=\frac{1}{2 y}-\sqrt{\frac{1}{4 y^{2}}-1}\) and the line \(x=1\) in the first quadrant. (Hint: Express \(y\) in terms of \(x\).)

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