Deriving Vr and V(sub-theta) from Kepler's second law and

LordCalculus
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Deriving Vr and V(sub-theta) from Kepler's second law and...

Homework Statement



Beginning with r=[a(1-e2)]/(1+e*cos \theta) and Kepler's second law, derive general expressions for vr and v\theta for a mass m1 in an elliptical orbit about a second mass m2. The final answers should be functions of P, e, a, and \theta only.

P=orbital period
e=eccentricity
a=semimajor axis

That's supposed to be v(subtheta) and cosine of theta!

Homework Equations



A'(t)=L/(2*\mu)
 
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v_\theta, understood. What have you done so far and where exactly did you get stuck?
 


Not far at all. I don't even know where to begin. If you do, then please start me off. Thanks!
 


Well, here would be my first thought: you have some information about position, and you are asked to find velocity. What does that tell you?
 

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