First what you should know is that: i = root (-1) We note that in this case the exponent is odd. So we can rewrite the expression as: i ^ 13 = (i ^ 2) * (i ^ 2) * (i ^ 2) * (i ^ 2) * (i ^ 2) * (i ^ 2) * i i ^ 13 = (- 1) * (- 1) * (- 1) * (- 1) * (- 1) * (- 1) * i i ^ 13 = (1) * i i ^ 13 = i Answer: the simplified form of i ^ 13 is: D. i