Can the Length of a Curve be Simplified Using Trigonometric Identities?

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SUMMARY

The discussion focuses on simplifying the integral for the length of the curve defined by the polar equation r = (1 + cos(2θ))^(1/2) over the interval from -π/2 to π/2. The length is calculated using the formula L = ∫ sqrt(r² + (dr/dθ)²) dθ, where dr/dθ is determined to be -sin(2θ) - sin(2θ)cos(2θ). Participants suggest utilizing trigonometric identities to simplify the integral, emphasizing the importance of recognizing patterns in trigonometric functions to facilitate easier integration.

PREREQUISITES
  • Understanding of polar coordinates and polar equations
  • Familiarity with integral calculus, specifically arc length calculations
  • Knowledge of trigonometric identities and their applications
  • Ability to differentiate functions with respect to θ
NEXT STEPS
  • Review trigonometric identities relevant to cos(2θ) and their simplifications
  • Practice calculating arc length for various polar curves
  • Explore integration techniques for complex functions involving square roots
  • Study the application of substitution methods in integral calculus
USEFUL FOR

Students studying calculus, particularly those focusing on polar coordinates and arc length, as well as educators seeking to enhance their teaching of integration techniques.

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Homework Statement



length of curve r=(1+cos(2 theta))^(1/2) from -pi/2..pi/2

Homework Equations



L= integral sqrt(r2+(dr/d(theta))2

dr/d(theta)= -sin(2theta)-sin(2theta)cos(2theta)

The Attempt at a Solution


this integral seems ways to complicated is there something to simplify it?

dr/d(theta)= -sin(2theta)-sin(2theta)cos(2theta)
then squaring it and adding (1+cos(2 theta))
seems really hard to integrate. So if someone could point out what I'm doing wrong, that would be nice. thanks.
 
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When you see cos 2θ that should remind you of something - if not look up a table of trig identities, or even work it out - and I think you can simplify this problem.
 

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