$$$\sqrt{5}\cdot \left\langle - \frac{\sqrt{5} \cos{\left(t \right)}}{5}, - \frac{\sqrt{5} \sin{\left(t \right)}}{5}, 0\right\rangle$$$

Calculate $$$\sqrt{5}\cdot \left\langle - \frac{\sqrt{5} \cos{\left(t \right)}}{5}, - \frac{\sqrt{5} \sin{\left(t \right)}}{5}, 0\right\rangle$$$.

Multiply each coordinate of the vector by the scalar:

$$${\color{Chocolate}\left(\sqrt{5}\right)}\cdot \left\langle - \frac{\sqrt{5} \cos{\left(t \right)}}{5}, - \frac{\sqrt{5} \sin{\left(t \right)}}{5}, 0\right\rangle = \left\langle {\color{Chocolate}\left(\sqrt{5}\right)}\cdot \left(- \frac{\sqrt{5} \cos{\left(t \right)}}{5}\right), {\color{Chocolate}\left(\sqrt{5}\right)}\cdot \left(- \frac{\sqrt{5} \sin{\left(t \right)}}{5}\right), {\color{Chocolate}\left(\sqrt{5}\right)}\cdot \left(0\right)\right\rangle = \left\langle - \cos{\left(t \right)}, - \sin{\left(t \right)}, 0\right\rangle$$$

$$$\sqrt{5}\cdot \left\langle - \frac{\sqrt{5} \cos{\left(t \right)}}{5}, - \frac{\sqrt{5} \sin{\left(t \right)}}{5}, 0\right\rangle = \left\langle - \cos{\left(t \right)}, - \sin{\left(t \right)}, 0\right\rangle$$$A