Answer: Option B.
Step-by-step explanation:
We want to find the value of i^51
We know that
i^1 = i
i^2 = -1
i^3 = -i
i^4 = 1
and it repeats with a period of 4, so i^5 = i^(1 + 4) = i^1= i, and so on.
so we can write it as:
x + n*4 = 51
where n is an integer number, and x is a number between 1 and 4.
clearly n must be an odd number, so we can try:
if x = 1.
1 + n*4 = 51
n*4 = 50
n = 50/4 = 12.5
This is not the solution for x, because n must be an integer number.
Now suppose x = 3.
3 + 4*n = 51
4*n = 48
n = 48/4 = 12
Then x is equal to 3, this means that:
i^51 = i^3*i^4*12 = i^3 = -i
The correct option is B
