Question: Can't assume on a variable

I get quite an annoying "bug" that messes up all the presentation aspect of my document.

I want to assume some variable is real so that calculation are simplified at several parts of the document.


But I get this:


Whener I use U__LL I always end up with this ugly form that would make anybody think U__LL is multiplied by itself.

How do I get around this?

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