.simplify_full() doesn't simplify an obvious trigonometric expression

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Ah, thank you! I've just read canonicalize_radical docs and it looks unsafe to use blindly. I experimented with it a little and reproduced a problem: ( (sin(x)-2) * sqrt( sin(x) / (sin(x)^2 - 4*sin(x) + 4) ) ).canonicalize_radical() becomes "sqrt(sin(x))" while it should be "-sqrt(sin(x))". I wonder if there's a way to tell it the sign to simplify sqrt()... But that should probably be another question. Thanks for your answer!

Yes, I think the "unsafe to use blindly" aspect was one reason for removing "canonicalize_radical" (which at the time was called "simplify_radical") from "simplify_full", in Sage Trac ticket 12737.

The sign issue is a recurring discussion which every time leads to a debate about what "sqrt" stands for: a multivalued function from the complex numbers to the complex numbers, or a single-valued function from the non-negative reals to the non-negative reals.

Thanks for the link and details! Personally I'd say sqrt() is a single-valued conditional function, and its symbolic representation depends on the sign of its argument, like, sqrt(x^2) = {x if x>=0; -x if x<0 }. It's just in my case the sign was known, so I hoped sage would guess that... Anyway, I posted that as a separate "canonicalize_radical produces incorrect result" question. I hope it makes sense.