How do you think sine and inverse sine are related?
edit: Ok it seems this isn't enough to grab your attention. For #1) you can also think of it as . So if x is an angle, -1 is a ratio. That is obviously simplified though, since the ratio is of (opposite)/(adjacent). Thus must be that either the opposite leg is 1 or 1 and that the adjacent leg is 1 or -1, but they can't both be the same sign, or the ratio would be positive.