Question

If i = sqrt -1 what is the value of i3

A. -1
B. i
C. 1
D. -i

Answer 1

i^3 = i * i * i = i^2 * i = -1 * i = -i Answer

Its D

Answer 2

The value of i3 is equal to D. -i

Explanation:

We can find the answer by taking the definition of i :

i = sqrt(-1) (1)

i ^2 = (sqrt(-1)) ^2 = -1 (2) because square root and squaring are inverse operations

so from (2)

i ^3= i ^2* i = -1*i = -i

So -i is the final answer or – (sqrt(-1)) which is the same