Math Problem Statement

integrate (lnx)/x with bounds infinity,1

Solution

To evaluate the integral 1ln(x)xdx\int_{1}^{\infty} \frac{\ln(x)}{x} \, dx, we'll go through the following steps:

  1. Integral Setup: I=1ln(x)xdxI = \int_{1}^{\infty} \frac{\ln(x)}{x} \, dx

  2. Substitution: Let u=ln(x)u = \ln(x), so du=1xdxdu = \frac{1}{x} \, dx.

    When x=1x = 1, u=ln(1)=0u = \ln(1) = 0.

    When xx \to \infty, uu \to \infty.

    The integral now becomes: I=0uduI = \int_{0}^{\infty} u \, du

  3. Evaluate the Integral: The integral of uu with respect to uu is straightforward: I=u220I = \left. \frac{u^2}{2} \right|_{0}^{\infty}

    Evaluating this: I=limuu22022=I = \lim_{u \to \infty} \frac{u^2}{2} - \frac{0^2}{2} = \infty

The integral diverges, meaning it does not converge to a finite value. Therefore:

1ln(x)xdx diverges.\int_{1}^{\infty} \frac{\ln(x)}{x} \, dx \text{ diverges.}

Would you like further details or have any questions?

Here are 5 related questions for further exploration:

  1. What is an example of a similar integral that converges?
  2. How can you determine whether an improper integral converges?
  3. What is the integral of 1xln(x)\frac{1}{x} \ln(x) over a finite interval, such as [1,e][1, e]?
  4. How does substitution affect the bounds of integration?
  5. Can we use any other techniques, like integration by parts, to solve this integral?

Tip: When dealing with improper integrals, always check for divergence by evaluating limits, especially as the variable approaches infinity or a point of discontinuity.

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Math Problem Analysis

Mathematical Concepts

Calculus
Improper Integrals

Formulas

Substitution method for integrals

Theorems

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Suitable Grade Level

Undergraduate