Integrating to find the length of a Cardiot Curve

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SUMMARY

The discussion focuses on calculating the length of a cardiot curve defined by the polar equation r = 1 + cos(Θ). The formula for the length of the curve is given as L = 2 ∫√[(r^2(Θ)) + (dr/dΘ)^2] dΘ, with the integration limits set from 0 to π. A key simplification involves rewriting the integral as ∫√[2 + 2cos(Θ)] dΘ, which can be further transformed using the identity (1 + cos(Θ))/2 = cos²(Θ/2) to facilitate integration.

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Jim4592
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Homework Statement


find the length of the cardiot r = 1+cos(Θ)

I'm going to use { as the integral sign
all integrals are definite between 0 and Pi

Homework Equations


L = 2 {sqrt[(r^2(Θ))+(dr/dΘ)^2]dΘ


The Attempt at a Solution


L=2* {sqrt[2+2cos(Θ)] dΘ

I'm having a really hard time trying to integrate sqrt[2+2cos(Θ)] dΘ and was hoping someone could explain to me how you integrate that.

Thanks.
 
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Personally, I would start by doing

[tex] \int_0^\pi \sqrt{2 + 2\cos\theta} \, d\theta <br /> = \sqrt{2}\int_0^\pi \sqrt{1 + \cos\theta}\, d\theta.[/tex]

It's totally not necessary, but it sort of simplifies things. Then you want to use the identity
[tex] \frac{1 + \cos\theta}{2} = \cos^2\frac{\theta}{2}[/tex]

Multiply both sides of that identity by 2, then you'll have something a little nicer to work with..
 

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