## Precalculus: Mathematics for Calculus, 7th Edition

$\dfrac{1}{i}=-i$
$\dfrac{1}{i}$ Multiply the fraction by $\dfrac{-i}{-i}$: $\Big(\dfrac{1}{i}\Big)\Big(\dfrac{-i}{-i}\Big)=\dfrac{-i}{-i^{2}}$ We know that $i^{2}=-1$, so we get: $\dfrac{-i}{-(-1)}=\dfrac{-i}{1}=-i$