Math Problem Statement

In the figure below, 𝑅 is the shaded region in the first quadrant bounded by the graph of 𝑦 = 4ln⁑(3 βˆ’ π‘₯), the horizontal line 𝑦 = 6, and the vertical line π‘₯ = 2. Find the area of 𝑅.

Solution

To find the area of the region RR, we need to set up the integral that represents the area bounded by the curve y=4ln⁑(3βˆ’x)y = 4\ln(3 - x), the line y=6y = 6, and the vertical line x=2x = 2.

Steps:

  1. Determine the bounds:

    • The curve y=4ln⁑(3βˆ’x)y = 4\ln(3 - x) intersects the horizontal line y=6y = 6 at a certain point. We need to solve for the intersection to find the upper bound for the region.
  2. Solve for the intersection: Set 4ln⁑(3βˆ’x)=64\ln(3 - x) = 6. ln⁑(3βˆ’x)=64=1.5\ln(3 - x) = \frac{6}{4} = 1.5 Now exponentiate both sides to eliminate the logarithm: 3βˆ’x=e1.53 - x = e^{1.5} Solving for xx: x=3βˆ’e1.5x = 3 - e^{1.5}

  3. Set up the integral: The area AA is given by the integral of the difference between the upper curve y=6y = 6 and the lower curve y=4ln⁑(3βˆ’x)y = 4\ln(3 - x), over the interval from x=0x = 0 to x=2x = 2: A=∫02(6βˆ’4ln⁑(3βˆ’x)) dxA = \int_0^2 \left( 6 - 4\ln(3 - x) \right) \, dx

  4. Evaluate the integral:

Let's compute the integral.

A=∫026 dxβˆ’βˆ«024ln⁑(3βˆ’x) dxA = \int_0^2 6 \, dx - \int_0^2 4 \ln(3 - x) \, dx

We'll evaluate these two integrals separately.

First integral:

∫026 dx=6x∣02=6(2)βˆ’6(0)=12\int_0^2 6 \, dx = 6x \bigg|_0^2 = 6(2) - 6(0) = 12

Second integral:

We use substitution for the second integral. Let u=3βˆ’xu = 3 - x, so du=βˆ’dxdu = -dx, and when x=0x = 0, u=3u = 3, and when x=2x = 2, u=1u = 1.

Now the integral becomes: βˆ’4∫31ln⁑(u) du-4 \int_3^1 \ln(u) \, du This simplifies to: 4∫13ln⁑(u) du4 \int_1^3 \ln(u) \, du The integral of ln⁑(u)\ln(u) is uln⁑(u)βˆ’uu \ln(u) - u, so: 4[uln⁑(u)βˆ’u]134 \left[ u \ln(u) - u \right]_1^3 Evaluating at the limits: 4[3ln⁑(3)βˆ’3βˆ’(1ln⁑(1)βˆ’1)]4 \left[ 3 \ln(3) - 3 - (1 \ln(1) - 1) \right] Since ln⁑(1)=0\ln(1) = 0, we get: [ 4 \left[ 3 \ln(3) - 3 + 1 \right] = 4 \left[ 3 \ln(3) - 2 \right] ] So, the second integral is: 4(3ln⁑(3)βˆ’2)=12ln⁑(3)βˆ’84(3 \ln(3) - 2) = 12 \ln(3) - 8

Final area calculation:

Now, combine the results: A=12βˆ’(12ln⁑(3)βˆ’8)A = 12 - (12 \ln(3) - 8) A=12βˆ’12ln⁑(3)+8A = 12 - 12 \ln(3) + 8 A=20βˆ’12ln⁑(3)A = 20 - 12 \ln(3)

Thus, the area of the region RR is: A=20βˆ’12ln⁑(3)A = 20 - 12 \ln(3)

Let me know if you need any further details or clarifications!

Related questions:

  1. How do logarithmic functions affect the shape of a graph?
  2. What are other common methods for solving integrals involving logarithms?
  3. Can you explain the substitution method in more detail?
  4. How does the area under a curve relate to real-world applications like physics or economics?
  5. How would you compute the area between two curves instead of just one?

Tip: Always check the limits of integration carefully, especially when solving for intersections or using substitution.

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Math Problem Analysis

Mathematical Concepts

Integration
Logarithmic Functions
Area under a curve
Definite Integrals

Formulas

Area under a curve: A = ∫ (upper curve - lower curve) dx

Theorems

Logarithmic Integration
Substitution Method

Suitable Grade Level

Grades 11-12