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Integrate 1x4x24dx\int \frac{1}{x^{4}\sqrt{x^{2}-4}}\,dx

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Q. Integrate 1x4x24dx\int \frac{1}{x^{4}\sqrt{x^{2}-4}}\,dx
  1. Simplify Integral: Let's start by simplifying the integral if possible. We have the integral: \newline1x4x24dx\int \frac{1}{x^{4}\sqrt{x^{2}-4}}\,dx\newlineThis integral does not simplify easily, so we will need to use a substitution to make it more manageable. We can try a trigonometric substitution since we have a square root of a quadratic expression.
  2. Trigonometric Substitution: We will use the substitution x=2sec(θ)x = 2\sec(\theta), which implies dx=2sec(θ)tan(θ)dθdx = 2\sec(\theta)\tan(\theta)d\theta. This substitution is chosen because it will simplify the square root in the denominator. The expression x24x^2 - 4 becomes (2sec(θ))24=4sec2(θ)4=4(tan2(θ))(2\sec(\theta))^2 - 4 = 4\sec^2(\theta) - 4 = 4(\tan^2(\theta)).
  3. Substitute xx and dxdx: Now we substitute xx and dxdx in the integral:\newline1x4x24dx=1(2sec(θ))44tan2(θ)(2sec(θ)tan(θ)dθ)\int \frac{1}{x^{4}\sqrt{x^{2}-4}}dx = \int \frac{1}{(2\sec(\theta))^{4}\sqrt{4\tan^2(\theta)}}(2\sec(\theta)\tan(\theta)d\theta)\newlineSimplify the integral:\newline=116sec4(θ)2tan(θ)(2sec(θ)tan(θ)dθ)= \int \frac{1}{16\sec^{4}(\theta)2\tan(\theta)}(2\sec(\theta)\tan(\theta)d\theta)\newline=132sec3(θ)tan2(θ)dθ= \int \frac{1}{32\sec^{3}(\theta)\tan^2(\theta)}d\theta
  4. Simplify Integral Further: We can simplify the integral further by using the identity sec2(θ)tan2(θ)=1\sec^2(\theta) - \tan^2(\theta) = 1, which gives us sec2(θ)=1+tan2(θ)\sec^2(\theta) = 1 + \tan^2(\theta). Therefore, sec3(θ)=sec(θ)(1+tan2(θ))\sec^3(\theta) = \sec(\theta)(1 + \tan^2(\theta)).\newlineThe integral becomes:\newline=132sec(θ)(1+tan2(θ))tan2(θ)dθ= \int \frac{1}{32\sec(\theta)(1 + \tan^2(\theta))\tan^2(\theta)}d\theta\newline=132(1+tan2(θ))tan2(θ)sec(θ)dθ= \int \frac{1}{32(1 + \tan^2(\theta))\tan^2(\theta)\sec(\theta)}d\theta
  5. Make Another Substitution: Now, we can make another substitution to simplify the integral further. Let u=tan(θ)u = \tan(\theta), which implies du=sec2(θ)dθdu = \sec^2(\theta)d\theta. Substituting these into the integral, we get:\newline=132(1+u2)u2du= \int \frac{1}{32(1 + u^2)u^2}du
  6. Integrate Using Partial Fractions: The integral is now in a form that we can integrate using partial fractions. However, the denominator is a product of a quadratic term and a squared term, which makes partial fractions complex. Instead, we can try to integrate by parts or look for another substitution or method.
  7. Review and Consider Alternatives: Upon reviewing the integral, it seems that a direct integration approach is not straightforward. We may need to revisit our substitution strategy or consider an alternative method to solve this integral. At this point, we have not made a math error, but we have reached an impasse in our solution strategy.

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