Math Problem Statement

use integration to find the average value of A(t) = 3/t between values 2 and 8

Solution

To find the average value of the function A(t)=3tA(t) = \frac{3}{t} between t=2t = 2 and t=8t = 8, we can use the formula for the average value of a function over an interval [a,b][a, b]:

Average value of A(t)=1baabA(t)dt\text{Average value of } A(t) = \frac{1}{b - a} \int_{a}^{b} A(t) \, dt

Here, A(t)=3tA(t) = \frac{3}{t}, a=2a = 2, and b=8b = 8. So, the formula becomes:

Average value=182283tdt\text{Average value} = \frac{1}{8 - 2} \int_{2}^{8} \frac{3}{t} \, dt

Step 1: Set up the integral

Average value=16283tdt\text{Average value} = \frac{1}{6} \int_{2}^{8} \frac{3}{t} \, dt

Step 2: Solve the integral

The integral of 1t\frac{1}{t} is lnt\ln|t|. So, we can solve the integral as follows:

283tdt=3281tdt=3[lnt]28\int_{2}^{8} \frac{3}{t} \, dt = 3 \int_{2}^{8} \frac{1}{t} \, dt = 3 [\ln|t|]_{2}^{8}

Evaluating the definite integral:

3[ln(8)ln(2)]=3ln(82)=3ln(4)3 [\ln(8) - \ln(2)] = 3 \ln \left(\frac{8}{2}\right) = 3 \ln(4)

Since ln(4)=2ln(2)\ln(4) = 2 \ln(2), we get:

3ln(4)=6ln(2)3 \ln(4) = 6 \ln(2)

Step 3: Calculate the average value

Now substitute the result of the integral back into the formula for the average value:

Average value=16×6ln(2)=ln(2)\text{Average value} = \frac{1}{6} \times 6 \ln(2) = \ln(2)

Thus, the average value of A(t)=3tA(t) = \frac{3}{t} between t=2t = 2 and t=8t = 8 is:

ln(2)\boxed{\ln(2)}

Would you like more details, or do you have any questions?


Here are 5 related questions to explore further:

  1. How do you find the average value of a quadratic function over an interval?
  2. Can you calculate the average value of A(t)=5t2A(t) = \frac{5}{t^2} over the same interval?
  3. What is the physical meaning of the average value of a function in an applied problem?
  4. How does the result change if we compute the average of A(t)=3tA(t) = \frac{3}{t} over a different interval?
  5. What if we replace 3t\frac{3}{t} with a trigonometric function like sin(t)\sin(t)? How do we compute the average then?

Tip: When solving integrals involving 1t\frac{1}{t}, remember that the result is always related to the natural logarithm function ln(t)\ln(t).

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Math Problem Analysis

Mathematical Concepts

Calculus
Integration
Average Value of a Function

Formulas

Average value of a function over an interval [a, b]: (1/(b - a)) * ∫[a to b] f(t) dt
Integral of 1/t: ∫(1/t) dt = ln|t|

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Grades 11-12 or early college calculus