$3-)M$ is a curve in $E^3$ with parametric equation

$$:$I{E}^3,$;$I=[0,2)$

$t(t)=(\frac{1}{\sqrt[\phantom{2}]{2}}cost,\frac{1}{\sqrt[\phantom{2}]{2}}cost,sint)$

Find Frenet vectors $($T$,$N$,$B$)$ at point $a(t).$