## Precalculus (10th Edition)

$i.$
If $v=ai+bj$ then the unit vector $u$ in the direction of $v$ is $u=\frac{v}{||v||}$, where $||v||=\sqrt{a^2+b^2}.$ $||v||=\sqrt{5^2+0^2}=\sqrt{25}=5.$ Hence $u=\frac{5i}{5}=i.$