Find the unit tangent vector $T(0)$ for the following parameterized curve. Then determine the unit tangent vector at the given value of t $.$

$r(t)=(8,5sin2t,5cos2t),$ for $0tx,t=\frac{}{4}$

Find the unit tangent vector.

$T(t)==(0,-sin2t)$

Determine the unit tangent vector at $t=\frac{}{4}.$

$T(\frac{x}{4})=(0,0,\frac{1}{-1})$