Newbie questions



I am investigating Maxima. Maybe I can use it for my teaching (at a German 
high school). Two questions:

1)
How do I set the floating point precision? I should like to calculate 2000 
digits sqrt(x) for example. (In Maple I should say Digits := 2000.)

2)
I should like to do something like this:

f(x) := sin(x);
f1(x) := diff(f(x),x);

but f1(x) is not a well defined function of course. (In Maple I should use 
"unapply" for this.)

TIA

-- 
JB