Chapter 7: Problem 38
Find the area of the region bounded by the graphs of the given equations. $$ y=2 \tan x, \quad y=0, \quad x=0, \quad x=\pi / 4 $$
Short Answer
Expert verified
The area is \( \ln 2 \).
Step by step solution
01
Identify the Bounded Region
The problem gives us the function \( y = 2 \tan x \), a horizontal line \( y = 0 \), and the vertical lines \( x = 0 \) and \( x = \frac{\pi}{4} \). These boundaries form a region under the curve of \( y = 2 \tan x \) between \( x = 0 \) and \( x = \frac{\pi}{4} \). We need to find the area under the curve from \( x = 0 \) to \( x = \frac{\pi}{4} \).
02
Set Up the Integral for the Area
The area under a curve \( y = f(x) \) from \( x = a \) to \( x = b \) is calculated using the integral \( \int_{a}^{b} f(x) \, dx \). In this case, the area we want is represented by the integral \( \int_{0}^{\pi/4} 2 \tan x \, dx \).
03
Integrate the Function
To find \( \int_{0}^{\pi/4} 2 \tan x \, dx \), first note that the integral of \( \tan x \) is \( -\ln|\cos x| \). Thus, \( \int 2 \tan x \, dx = 2 \left(-\ln|\cos x|\right) = -2 \ln|\cos x|\). Now compute the definite integral: \[ -2 \ln|\cos x| \Big|_{0}^{\pi/4}. \]
04
Evaluate the Integral at the Bounds
Evaluate \( -2 \ln|\cos x| \) at the bounds \( x = 0 \) and \( x = \frac{\pi}{4} \). When \( x = \frac{\pi}{4} \), \( \cos \frac{\pi}{4} = \frac{\sqrt{2}}{2} \), so \(-2 \ln \left( \frac{\sqrt{2}}{2} \right)\). When \( x = 0 \), \( \cos 0 = 1 \), so \( -2 \ln(1) = 0 \).
05
Simplify and Find the Area
Simplify \( -2 \ln \left( \frac{\sqrt{2}}{2} \right) \). Recall \( \ln \left( \frac{\sqrt{2}}{2} \right) = \ln \sqrt{2} - \ln 2 = \frac{1}{2} \ln 2 - \ln 2 = -\frac{1}{2} \ln 2 \). Hence, the area is \( 2 \times \left(-\left(-\frac{1}{2} \ln 2\right)\right) = \ln 2 \).
06
Conclude the Calculation
The area under the curve \( y = 2 \tan x \) from \( x = 0 \) to \( x = \frac{\pi}{4} \) with respect to the x-axis is \( \ln 2 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Definite Integral
The concept of a definite integral is fundamental in calculus, specifically when finding the area of a region under a curve. A definite integral is represented as \( \int_{a}^{b} f(x) \, dx \), where \( f(x) \) is a function and \( a \) and \( b \) are the limits of integration. In the exercise provided, we calculate the definite integral of the function \( y = 2 \tan x \) over the interval from \( x = 0 \) to \( x = \frac{\pi}{4} \).
This process involves evaluating the integral of the function over the given bounds. Unlike an indefinite integral, a definite integral results in a numerical value, which represents the net area between the function and the x-axis within these limits. Thus, the concept of definite integrals allows us to precisely quantify the area under a curve, enhancing our understanding of mathematical regions bounded by various functions.
This process involves evaluating the integral of the function over the given bounds. Unlike an indefinite integral, a definite integral results in a numerical value, which represents the net area between the function and the x-axis within these limits. Thus, the concept of definite integrals allows us to precisely quantify the area under a curve, enhancing our understanding of mathematical regions bounded by various functions.
Trigonometric Functions
Trigonometric functions, such as \( \tan x \), play a crucial role in many calculus problems. These functions relate the angles and sides of a triangle, but in calculus, they describe periodic oscillations and waveforms. In this exercise, the function \( y = 2 \tan x \) establishes a specific curve.
The \( tangent \) function displays a unique behavior; it has asymptotes where it approaches infinity, particularly near odd multiples of \( \frac{\pi}{2} \). This makes the range of \( \tan x \) discontinuous at these points. But within the interval from \( x = 0 \) to \( x = \frac{\pi}{4} \), the function behaves nicely and is continuous. This allows us to easily integrate it between the given range without encountering undefined regions.
The \( tangent \) function displays a unique behavior; it has asymptotes where it approaches infinity, particularly near odd multiples of \( \frac{\pi}{2} \). This makes the range of \( \tan x \) discontinuous at these points. But within the interval from \( x = 0 \) to \( x = \frac{\pi}{4} \), the function behaves nicely and is continuous. This allows us to easily integrate it between the given range without encountering undefined regions.
- The function is scaled by 2, modifying the amplitude but retaining its fundamental properties.
- Understanding these properties is vital for accurately evaluating the region bounded by such trigonometric functions.
Bounded Region
A bounded region describes a section of the plane confined by curves, lines, or axes, and is critical to understanding which area we need to compute. For the given problem, the region is "bounded" by:
- The curve given by \( y = 2 \tan x \).
- The horizontal line \( y = 0 \) (the x-axis).
- Vertical lines at \( x = 0 \) and \( x = \frac{\pi}{4} \).