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    http://www.thestudentroom.co.uk/show...4&postcount=18

    in that thread how does this come about in Q4?

    deltT / [2tan(deltpsi/2)] = T mu

    Finally we let A and B get close together, so that deltT and deltpsi become small:

    dT/d(psi) = T mu
    i dont get how if deltT and deltpsi become small then the equation reduces to dT/d(psi)
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    For small angles x (in radians), tanx is approximately x.
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    so then how comes its d(psi) and not 2d(psi) then? still doesnt make sense to me
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    (Original post by madhapper)
    so then how comes its d(psi) and not 2d(psi) then? still doesnt make sense to me
    Look at the series expansion of 2tan(x/2).

    You get:

    2tan(x/2) = x + (x^3)/12 + (x^5)/120 + ...

    So as for small value of x, 2tan(x/2) ~=~ x

    That is why the expression becomes dT/d(psi).

    Euclid
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    ah ok thanx alot!
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    (Original post by madhapper)
    so then how comes its d(psi) and not 2d(psi) then? still doesnt make sense to me
    cos the 2s cancel.
 
 
 
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