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    sorry to start another thread on this but i still don't get it!!

    the question: solve y+(axy)=b (where x represents cross product) for x in terms of a and b.

    what i did is as follows...

    i took the cros product of each side with a:
    axy+ax(axy)=axb
    ∴axy+axa+axy=axb
    ∴2axy=axb
    ∴y=0.5b

    why is this wrong and what is the right way? I have been told i should take dot product and scalar product of both sides, but i dont see how this helps.
    confused!!!
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    (Original post by realicetic)
    axy+ax(axy)=axb
    ∴axy+axa+axy=axb
    ∴2axy=axb
    ∴y=0.5b
    ax(axy) is not equal to axa + axy I dont think...
    axy = n|a||y|sinØ. Since a is perpendicular to n,then axn = |a|²|n||y|k roughly(K perp to n and a(is this y?)), which is not the same as axy.
    I havent done dot and cross in a while, but I suspect that you can do this:
    dot a to everything, then you obtain
    a.y+ a.(axy) = a.b
    Since a.y will produce a perpendicular vector to a, a.(axy) = 0. (as the angle between then is now 90°, cos 90 = 0).

    Hence a.y = a.b.
    You can do the rest if you can go further, cause my memory just ran out
 
 
 

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