I wonder if the comparison test would work, which you find a function similar to

the function which in this case you can do, someone correct me if I am wrong

since cosine is bounded by -1 and 1

so then

so in comparsion, you can say you function behaves like the function

, if you dont know the comparsion test, look it up it can prove helpful, if you find a function larger than your original then you the function you were given which is small will also converge, if you find a function smaller than the original diverges then the original will diverge, this does not apply to vice versa so now you can do

you should be able to take it from here