How can I do tan^-1, sin^-1 and cos^-1 in java?

Answer 1

you can read the documentation.
asin gives you sin^-1
As for the others,
cos^-1(x) = sin^-1√(1-x^2)
tan^-1(x)=sin^-1(x/√(1+x^2))
There may be atan2 -- don't recall.
Java docs are very good. Read them.
and so on.