Q. Evaluate the integral and express your answer in simplest form.∫xx2−251dxAnswer:
Recognize standard inverse trigonometric form: Recognize the integral as a standard inverse trigonometric form.The integral ∫xx2−251dx can be recognized as an inverse trigonometric integral because the denominator has the form of a2−u2, where a=5 and u=x. This suggests a substitution using the inverse trigonometric function secant.
Perform substitution with secant: Perform the substitution x=5sec(θ). Let x=5sec(θ), which implies dx=5sec(θ)tan(θ)dθ. We also need to express x2−25 in terms of θ. Since x=5sec(θ), we have x2−25=25sec2(θ)−25=25(tan2(θ))=5tan(θ).
Rewrite integral in terms of theta: Rewrite the integral in terms of θ. Substituting x and dx into the integral, we get ∫5sec(θ)⋅5tan(θ)1⋅5sec(θ)tan(θ)dθ. The 5's and sec(θ)tan(θ) cancel out, leaving us with ∫5tan(θ)1⋅5sec(θ)tan(θ)dθ=∫dθ.
Integrate with respect to theta: Integrate with respect to θ. The integral of dθ is simply θ. So we have ∫dθ=θ+C, where C is the constant of integration.
Back-substitute for x: Back-substitute to express the answer in terms of x.We originally let x=5sec(θ), so we need to solve for θ in terms of x. We have sec(θ)=5x, and taking the inverse secant of both sides gives us θ=sec−1(5x). Therefore, the integral in terms of x is sec−1(5x)+C.
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