1) arcsin[x2]
the domain is -1 <= x <= 1
range is 0 <= y <= pi/2, since x2 >= 0
x arccos[x]
-1 <= x <= 1
-pi <= y <= ? (i don't know if upper limit is solvable)
y = acrsin[tanx]
-1 <= tan[x] < 1
-pi/4 <= x <= pi/4
-pi/2 <= y <= pi/2
2) (keeping in mind the range of arctan)
let x = tan, -pi/2 < u < pi/2
arctan[tan]
= u
1/x = cot
cot = tan[pi/2 - u] = tan[-pi/2 - u]
arctan[tan[pi/2 - u]]
= pi/2 - u, if 0<= u < pi/2, x >= 0
or arctan[tan[-pi/2 -u]
= -pi/2 - u, if -pi/2 < u < 0, x<0
adding the two we get
actan[x] + arctan[1/x] = u + pi/2 - u
= pi/2 (x >=0)
actan[x] + arctan[1/x] = u - pi/2 - u
= -pi/2 (x < 0)