Integrating a trig function divided by a trig function

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SUMMARY

The discussion focuses on finding the arc length of the curve defined by the polar equation r=4/θ for the interval ∏/2 ≤ θ ≤ ∏. The arc length formula L is established as L= ∫ √(r^2 + (dr/dθ)^2) dθ. Participants explore the integral ∫ ((secx)^3/(tanx)^2) and reference the integral ∫ (secx)^3 = (1/2)sec(x)tan(x)+(1/2)ln|sec(x)+tan(x)|. The conversation highlights the complexity of using integration by parts and transforming the integral into a more manageable form involving sin and cos functions.

PREREQUISITES
  • Understanding of polar coordinates and arc length calculations
  • Familiarity with trigonometric identities and integrals
  • Knowledge of integration techniques, including integration by parts
  • Proficiency in calculus, specifically in handling complex integrals
NEXT STEPS
  • Study the derivation and applications of the arc length formula in polar coordinates
  • Learn advanced techniques for integrating trigonometric functions, particularly secant and tangent
  • Explore integration by parts with specific focus on trigonometric integrals
  • Practice transforming integrals using trigonometric identities to simplify calculations
USEFUL FOR

Students studying calculus, particularly those focusing on polar coordinates and integration techniques, as well as educators seeking to enhance their teaching methods in advanced mathematics.

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Homework Statement



Find the arc length of the curve r=4/θ, for ∏/2 ≤ θ ≤ ∏

Homework Equations



L= ∫ ds = ∫ √(r^2 + (dr/dθ)^2) dθ

The Attempt at a Solution



After some calculations, and letting θ = tanx, I now have to find ∫ ((secx)^3/(tanx)^2). I am not sure how to do this, but i have found online that ∫ (secx)^3 = (1/2)sec(x)tan(x)+(1/2)ln|sec(x)+tan(x)|. Using integration by parts and letting u = 1/(tan(x))^2= (cot(x))^2 and du/dx = -2cot(x).(cosec(x))^2 is looking very tedious. How do I solve this problem correctly?
 
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I don't see how you got sec^3(x). I get just sec(x) in the numerator.

Eventually, I reduce it to
\int \frac{sin^3(x)}{cos^2(x)}dx

Factor out a sin(x) to use with the dx and convert the remaining sin^2(x) to 1- cos^2(x).
 

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