Differential Equation: Solving for x in terms of θ | (3+cos2θ)dx/dθ = xsin2θ

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The discussion focuses on solving the differential equation (3 + cos 2θ) dx/dθ = x sin 2θ for x in terms of θ. The initial steps involve separating variables and applying a u-substitution where u = 3 + cos 2θ. The user correctly identifies the equation as first-order separable and sets up the integral dx/x = (sin 2θ)/(3 + cos 2θ) dθ. The reasoning behind the steps taken is validated, although arithmetic verification is left to the user. The conversation emphasizes the importance of proper substitution and integration techniques in solving the differential equation.
chwala
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Homework Statement


Solve and obtain an expression for x in terms of θ given ## (3+ cos 2θ) dx/dθ = x sin 2θ##

Homework Equations

The Attempt at a Solution


...##dx/x = ((sin 2θ)/(3+ cos 2θ))dθ## ,

let ##u = (3+cos 2θ)⇒ du/dθ= -2 sin 2θ##
thus

##∫dx/x = -1/2∫du/u ##...[/B]are my steps correct?i can solve from here
 
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You noticed that it was 1st order seperable, and proposed a u-substitution for the resulting RHS: well done.
I didn't check your arithmetic - you have to do that yourself - but the reasoning is sound so far.
 
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Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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