Question

The order of -i in the multiplicative group of 4^th roots of unity is …

(a) 4 

(b) 3 

(c) 2 

(d) 1

Answer 1

(a) 4

The roots of fourth roots of unity are 1, -1, i, -i 

The identity element is 1 

(-i)⁴ = i⁴ = 1 

Order of (-i) = 4.