Answer:
No solution
Step-by-step explanation:
We have
For the sum it is not correct to assume
Note that for
it is assumed and in your case for
In fact, considering a set we have
that satisfy
This means that, by definition
Therefore,
because the sum is empty.
For
we have other problems. Actually, this case is really bad.
Note that has no value. In fact, if we consider for the case
, the cosine function oscillates between , and therefore it is undefined. Thus, we cannot evaluate
and then
has no solution