Find the area of the region enclosed by the graphs of y = e^x, y = e^(-x), and y = 6. (Use symbolic notation and fractions where needed.)
Understand the Problem
The question is asking to find the area of the region enclosed by three graphs: y = e^x, y = e^(-x), and y = 6. This involves determining the points of intersection and then calculating the area between the curves using integration.
Answer
The area is given by $$ A = 24\ln(6) + \frac{7}{6} $$
Answer for screen readers
The area of the region enclosed by the graphs is
$$ A = 24\ln(6) + \frac{7}{6} $$
Steps to Solve
- Find Points of Intersection
First, we find where the graphs intersect by setting $y = e^x$ equal to $y = 6$.
$$ e^x = 6 $$
Taking the natural logarithm of both sides, we have
$$ x = \ln(6) $$
Next, we find where $y = e^{-x}$ intersects $y = 6$.
$$ e^{-x} = 6 $$
Taking the natural logarithm of both sides, we get
$$ -x = \ln(6) \quad \Rightarrow \quad x = -\ln(6) $$
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Set Up the Integral for Area Calculation
The area enclosed by the curves can be found by integrating the difference between the top curve $y = 6$ and the bottom curve $y = e^{x}$ from $x = -\ln(6)$ to $x = \ln(6)$, and then adding the area between $y = 6$ and $y = e^{-x}$.
The area $A$ can be expressed as:
$$ A = \int_{-\ln(6)}^{\ln(6)} (6 - e^x) , dx + \int_{-\ln(6)}^{\ln(6)} (6 - e^{-x}) , dx $$ -
Calculate Each Integral
Calculating the first integral:
$$ \int (6 - e^x) , dx = 6x - e^x $$
Now, evaluate from $-\ln(6)$ to $\ln(6)$:
$$ \left[ 6x - e^x \right]_{-\ln(6)}^{\ln(6)} = [6\ln(6) - 6] - [(-6\ln(6)) - \frac{1}{6}] $$
This simplifies to:
$$ A_1 = 6\ln(6) - 6 + 6\ln(6) + \frac{1}{6} = 12\ln(6) - 5 $$
Now, calculate the second integral:
$$ \int (6 - e^{-x}) , dx = 6x + e^{-x} $$
Evaluate using the same bounds:
$$ \left[ 6x + e^{-x} \right]_{-\ln(6)}^{\ln(6)} = [6\ln(6) + \frac{1}{6}] - [6(-\ln(6)) + 6] $$
This simplifies to:
$$ A_2 = 6\ln(6) + \frac{1}{6} + 6 + 6\ln(6) = 12\ln(6) + 6 + \frac{1}{6} $$
- Total Area Calculation
Combine both areas:
$$ A_{total} = A_1 + A_2 = (12\ln(6) - 5) + (12\ln(6) + 6 + \frac{1}{6}) $$
Combine like terms:
$$ A_{total} = 24\ln(6) + \frac{1}{6} + 1 $$
Thus, the total area is:
$$ A = 24\ln(6) + \frac{7}{6} $$
The area of the region enclosed by the graphs is
$$ A = 24\ln(6) + \frac{7}{6} $$
More Information
This area represents the total region bounded by the exponential functions $y = e^x$, $y = e^{-x}$, and the horizontal line $y = 6$. The use of natural logarithms reflects how exponential functions relate to logarithmic functions, emphasizing the interplay between growth and decay.
Tips
- Forgetting the bounds: Always ensure the limits of integration correspond to the points of intersection.
- Incorrect integration: Double-check the integration of exponential functions, particularly signs in front of them.
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