No! neither
, which is what I think you mean, nor
, which is what you actually wrote, is equal to
. The first
means "find the square root of x, then take the cosine of that number, then multiply it by itself 5 times". The second
means "find the square root of x, multiply that by 5, then take the cosine". The last
means "find the square root of x, find the cosine of it, then multiply by 5".
For example, if x= 4,
so that
(approximately) so that
, approximately. Of course,
. Of course,
so
.
Those are three different calculations giving three different answers.