Verified answer

i = (-1)^1/2

replace above into equation

=(-1)^1/2*19*9*8

=(-1)^684

=1

so i^2 = -1 , i^3= -i, i^4 = 1 ...hope u understood how they wer derived from i = sqrt(-1)..one aftr the other...

now i^19 = i^16 * i^3 = (i^4)^4 * (-i)= -i

so ((-i)^9)^8=(i^9)^8= i^ 8 = 1