i^7 = -i
keep those in mind when solving this kind of questions
i^1 = i
i^2 = -1
i^3 = -i
i^4 = 1
to find the answer you need to divide 7 by 4 and find the remainder.
the remainder is 3. so you use the one that’s to the 3rd power (i^3) which is equal to -i. if you want me to explain to you how to find the remainder using a scientific calculator let me know :)