Solution #29

Recall that i² = -1, i³ = -i, and i⁴ = 1. Thus i^-1 = i³ = -i.

So we have (i - i^-1)^-1 = (i - -i)^-1 = (2i)^-1 = (1/2)(i^-1) = (1/2)(-i) = -i/2.