Let sin-1i=x
then sinx=i
If x belongs to complex set then I think it is defined.
We know
sinx=(eix-e-ix)/2i= -i(eix-e-ix)/2
Suppose (eix-e-ix)/2= -1 and put eix=a
Then we get a2+2a-1=0
or a= -1(+or-)(

2)Consider a=((

2)-1)
e
ix=((

2)-1)
Taking log to the base e on both sides
we get x=[ln((

2)-1)]/i
If you are satisfied then I'm waiting for a salute!!!
Cheers!!!