I cannot for the life of me work this one out, I am getting very close, but I can't take it further, I must have made a mistake somewhere down the line, anyone mind checking my work? Couldn't get a hold of my prof today :(

Question: Show that .

Here's what I did.

I've been trying all sorts of ways to simplify it from here, but none have worked.

Thanks for your time!

Kasper