Math Problem Statement

\int_{1}^{4}\frac{\ln\left(x\right)}{x}dx

Solution

The given integral is:

14ln(x)xdx\int_{1}^{4} \frac{\ln(x)}{x} \, dx

This is a classic integral that can be solved using the technique of substitution.

  1. Recall the formula:

ln(x)xdx=(ln(x))22+C\int \frac{\ln(x)}{x} \, dx = \frac{(\ln(x))^2}{2} + C

Now, let's apply the limits of integration from 1 to 4.

  1. Evaluating the definite integral:

14ln(x)xdx=[(ln(x))22]14\int_{1}^{4} \frac{\ln(x)}{x} \, dx = \left[ \frac{(\ln(x))^2}{2} \right]_{1}^{4}

  1. Substitute the limits:

First, evaluate at the upper limit x=4x = 4:

(ln(4))22=(ln(22))22=(2ln(2))22=4(ln(2))22=2(ln(2))2\frac{(\ln(4))^2}{2} = \frac{(\ln(2^2))^2}{2} = \frac{(2\ln(2))^2}{2} = \frac{4(\ln(2))^2}{2} = 2(\ln(2))^2

Now, evaluate at the lower limit x=1x = 1:

(ln(1))22=022=0\frac{(\ln(1))^2}{2} = \frac{0^2}{2} = 0

  1. Final result:

14ln(x)xdx=2(ln(2))2\int_{1}^{4} \frac{\ln(x)}{x} \, dx = 2(\ln(2))^2

This is the exact value of the definite integral.


Would you like further details on any step? Here are 5 related questions for you to explore:

  1. How can substitution be used to solve integrals with different logarithmic functions?
  2. What is the significance of the natural logarithm in integration problems like this?
  3. How do we derive the integral ln(x)xdx\int \frac{\ln(x)}{x} dx?
  4. How does the method of integration by parts apply to similar integrals?
  5. What are the properties of definite integrals over logarithmic functions?

Tip: Integrals involving logarithmic functions often simplify using properties of logarithms, such as ln(ab)=bln(a)\ln(a^b) = b\ln(a).

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Math Problem Analysis

Mathematical Concepts

Integral Calculus
Logarithmic Functions
Definite Integrals

Formulas

\int \frac{\ln(x)}{x} dx = \frac{(\ln(x))^2}{2} + C

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

College-level Calculus