Answer :

The inverse cosine can never be outside the domain of [-1,1]. 3/2 is greater than 1, and so there can never be a corresponding angle the cosine of which would give you 3/2. The cosine of any angle can only result in a value between or equal to -1 and 1.

Hope this helps! :)

AL2006
It says that the cosine of  Θ  is 3/2 , but the cosine of an angle
can never be more than ' 1 '.