What is the simplified form of i13? a. -i b. 1 c. -1 d. i

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
  
 the simplified form of i ^ 13 is: 
 D.i