Answer
$i$
Work Step by Step
The magnitude of any vector (let us say $v$) can be determined using the formula
$||v||=\sqrt{p^2+q^2+r^2} $
and the unit vector $u$ in the same direction as $v$ can be found as: $u=\dfrac{v}{||v||}$
Therefore, the unit vector $u$ in the same direction as $v$ is:
$u=\dfrac{5i}{\sqrt {(5)^2+(0)^2+(0)^2}} =\dfrac{5i}{\sqrt {25}} =
\dfrac{5i}{5}=i$
