Hey all. So I think I've been trying to figure this out longer than I should, that is why I am here now. I was reading an ieee paper and have been pondering a missing proof (the paper deems this proof too easy to show, literally... I must be really stupid or something). It is a simple question. How did they get from equation (21) to equation (49). I actually prefer hints rather than a definite answer, but of course anything is appreciated at this point.(adsbygoogle = window.adsbygoogle || []).push({});

Here is equation (21):

And here is equation (49), along with some verbiage:

I have tried many things with no avail. I have also tried working backwards, starting from (49), I did get nice equations, but nothing that has gotten me from (21) to (49). I can post this nice equation I speak of, but I doubt it would help.

If you are interested, here is a link to the paper I am reading.

Thank you for your time.

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# A What is the identity?

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