Question

Simplify i^18
A. 1
B. -1
C. i
D. -i

Answer 1

-1

Answer 2

\[\Large i^1 = i \\ \Large i^2 = -1 \\ \Large i^3 = -i \\ \Large i^4 = 1\]
\[\Large18/4 = 4\operatorname{r}2 ~\longrightarrow~ i^{18} = i^2 = \boxed{-1}\]