As far as I can tell, the only problems come from evaluating some
of the inverse trigonometric functions on the branch cuts. Off
the cuts, they are OK. So it goes -- standing with one foot on
and one foot off El Capitan, you're begging for trouble. Yes,
all this stuff should be standardized, but it's maybe not as bad
as you might think; after all the condition number along the branch
cuts is infinite.
Barton
For Maxima users outside the US, El Capitan is a huge nearly
vertical cliff in California.