Is there somewhere in this formula?
With no "i" Demoivre's theorem does not apply. I see nothing to do but evaluate that using a calculator.
If that was supposed to be
then use the fact that
Of course, . You should recognize that refers to an angle in a right triangle with "opposite side" 5 and "hypotenuse" 13. What is the length of the other leg? So what are the sine and cosine?