Hi I was just wondering how do you do inverse functions?

example: Sin^-1 (5pi/6)
Sin^-1 (3pi/2)

Why does most of the answers only have 1 answer and is out of "RANGE"?

2 answers

Sin^-1 sqrt(3)/2
Has only 1 answer. Why is 2pi/3 out of the range?
The interval for the range of sin(x) is
[-1,1].

5Ï€/6=2.61... > 1
and similarly
3Ï€/2=4.71... >1

sin-1(sqrt(3)/2)
= π/3