The inverse sine function

can only operate on numbers in the domain of

.
For the given function

, the only restriction is that

, which you must solve to find that the domain is actually

or, in interval notation,

.
Had the question asked for the domain of
})
, you would have needed to solve

to get a domain of

.
Finally, had the question asked for the domain of
}}{x^2-4})
, you would still have needed to solve

but subject to the additional constraint that

, producing a domain of
\cup\left(-2, -\sqrt{3}\right]\cup\left[\sqrt{3}, 2\right)\cup\left(2, \sqrt{5}\right])
.