Need help to solve one differential equation

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SUMMARY

The discussion focuses on solving the differential equation \(\frac{d^2 \theta}{dt^2}-A\sin(\theta)-\frac{B^2 \cos(\theta)}{\sin^3(\theta)}=0\), which arises from the brachistochronic motion on the surface of a sphere. A participant suggests using the relationship \(d^2\theta/dt^2 = d\omega/dt = d\omega/d\theta d\theta/dt = \omega d\omega/d\theta\) to transform the equation. This leads to the expression \(d(\omega^2)/d\theta = 2A\sin(\theta) + 2B\cot(\theta)\csc^2(\theta)\) as a potential method for solving the equation.

PREREQUISITES
  • Understanding of differential equations, specifically second-order equations.
  • Familiarity with trigonometric functions and their derivatives.
  • Knowledge of the brachistochronic problem in physics.
  • Basic calculus, particularly techniques involving integration and differentiation.
NEXT STEPS
  • Study methods for solving second-order differential equations.
  • Research the brachistochronic motion and its applications in physics.
  • Learn about the use of trigonometric identities in differential equations.
  • Explore numerical methods for approximating solutions to complex differential equations.
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Students and professionals in mathematics and physics, particularly those interested in differential equations and classical mechanics, will benefit from this discussion.

TimJ
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Does anybody know how to solve this differential equation:

<br /> \frac{d^2 \theta}{dt^2}-A\sin(\theta)- <br /> \frac{B^2 \cos(\theta)}{ \sin^3(\theta) }=0<br />

This is an equation that i get from the brachistochronic motion on the surface of a sphere.
 
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Welcome to PF!

Hi TimJ! Welcome to PF! :smile:

(have a theta: θ and an omega: ω :wink:)
TimJ said:
<br /> \frac{d^2 \theta}{dt^2}-A\sin(\theta)- <br /> \frac{B^2 \cos(\theta)}{ \sin^3(\theta) }=0<br />

Try writing d2θ/dt2 = dω/dt = dω/dθ dθ/dt = ω dω/dθ = 1/2 d(ω2)dθ,

so d(ω2)/dθ = 2Asinθ + 2Bcotθcosec2θ :wink:
 
Thank you for your help.
 

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