Transformations and their inverse

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The discussion focuses on the relationship between transformations and their inverses in the context of functions and Jacobian matrices. It highlights the challenge of finding inverse functions and the desire for shortcuts in this process. A key point made is that the Jacobian of the inverse transformation is the reciprocal of the Jacobian of the original transformation. This relationship is confirmed as a useful fact for understanding transformations. The conversation emphasizes the importance of the Jacobian in analyzing transformations and their inverses.
FunkyDwarf
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Hey guys

This isn't related to a particular question but i thought might be too specific for the general forum so here we go...

If you have a function f(x,y) such that u = f(x) and v= g(x) and you have some transformation T(u,v) i know you can find the inverse by getting x and y in terms of u and v and getting the Jacobian matrix etc. BUT if you can't (or like me too lazy/stupid) to be able to find f-1 or g-1 then is there a shortcut? I ask this knowing half the answer: i remembe there being a relation between the jacobian for a transform and its inverse but i don't know what it is.

The reason i ask the rest of the shpeel before it is to make sure I am understanding that correctly as well.

Thanks
-G
 
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There's no shortcut...
 
Ah finally found what i think it is:
Remark: A useful fact is that the Jacobian of the inverse transformation is the reciprocal of the Jacobian of the original transformation.
Is this not true?
 
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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