Math Problem Statement

Evaluate the integral \( \int_2^3 \frac{dx}{(x-1)^2 \sqrt{x^2 - 2x}} \).

Solution

To solve the given integral:

23dx(x1)2x22x\int_2^3 \frac{dx}{(x-1)^2 \sqrt{x^2 - 2x}}

Steps to Solve:

  1. Simplify the Radicand: Rewrite x22xx^2 - 2x as x(x2)x(x - 2), so the integrand becomes: 23dx(x1)2x(x2).\int_2^3 \frac{dx}{(x-1)^2 \sqrt{x(x - 2)}}.

  2. Substitution: Let u=x1u = x - 1, so x=u+1x = u + 1 and dx=dudx = du. The limits of integration change as follows:

    • When x=2x = 2, u=1u = 1,
    • When x=3x = 3, u=2u = 2.

    Substitute into the integral: 23dx(x1)2x(x2)=12duu2(u+1)(u1).\int_2^3 \frac{dx}{(x-1)^2 \sqrt{x(x - 2)}} = \int_1^2 \frac{du}{u^2 \sqrt{(u + 1)(u - 1)}}.

  3. Simplify Further: The square root simplifies as: (u+1)(u1)=u21.\sqrt{(u + 1)(u - 1)} = \sqrt{u^2 - 1}.

    The integral now becomes: 12duu2u21.\int_1^2 \frac{du}{u^2 \sqrt{u^2 - 1}}.

  4. Use Trigonometric Substitution: Let u=secθu = \sec\theta, so du=secθtanθdθdu = \sec\theta\tan\theta \, d\theta and u21=tanθ\sqrt{u^2 - 1} = \tan\theta. The limits of integration change:

    • When u=1u = 1, θ=0\theta = 0,
    • When u=2u = 2, θ=sec1(2)\theta = \sec^{-1}(2).

    Substituting these, the integral becomes: 0sec1(2)secθtanθdθsec2θtanθ=0sec1(2)dθsecθ.\int_0^{\sec^{-1}(2)} \frac{\sec\theta\tan\theta \, d\theta}{\sec^2\theta \tan\theta} = \int_0^{\sec^{-1}(2)} \frac{d\theta}{\sec\theta}.

  5. Simplify: Since 1secθ=cosθ\frac{1}{\sec\theta} = \cos\theta, the integral simplifies to: 0sec1(2)cosθdθ.\int_0^{\sec^{-1}(2)} \cos\theta \, d\theta.

  6. Evaluate the Integral: The integral of cosθ\cos\theta is sinθ\sin\theta. Thus: 0sec1(2)cosθdθ=sinθ0sec1(2).\int_0^{\sec^{-1}(2)} \cos\theta \, d\theta = \sin\theta \Big|_0^{\sec^{-1}(2)}.

    Substitute the limits:

    • At θ=sec1(2)\theta = \sec^{-1}(2), sinθ=32\sin\theta = \frac{\sqrt{3}}{2},
    • At θ=0\theta = 0, sinθ=0\sin\theta = 0.

    So the result is: 320=32.\frac{\sqrt{3}}{2} - 0 = \frac{\sqrt{3}}{2}.

Final Answer:

32\boxed{\frac{\sqrt{3}}{2}}

Would you like further clarification or more detailed steps? Here are related questions to expand your understanding:

  1. What is the importance of substitution in evaluating complex integrals?
  2. How does trigonometric substitution simplify square roots in integrals?
  3. Could other substitutions (e.g., hyperbolic) solve this problem differently?
  4. How can the limits of integration be verified after substitution?
  5. What are the conditions under which trigonometric substitution is ideal?

Tip: Always verify that your substitution simplifies both the integr

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Math Problem Analysis

Mathematical Concepts

Integral Calculus
Trigonometric Substitution
Definite Integrals

Formulas

\( \int \cos\theta \, d\theta = \sin\theta + C \)
Trigonometric substitution: \( u = \sec\theta \)
Radical simplification: \( \sqrt{x^2 - 2x} = \sqrt{x(x - 2)} \)

Theorems

Fundamental Theorem of Calculus

Suitable Grade Level

Undergraduate Calculus