please help #5find the curve's unit tangent vector and length of theindicated portion of the curve. (5) \( \mathbf{r}(t)=\left(\cos ^{3} tight) \mathbf{j}+\left(\sin ^{3} tight) \mathbf{k}, \quad 0 \leq t \leq \pi / 2 \) 6. \( \mathbf{r}(t)=6 t^{3} \mathbf{i}-2 t^{3} \mathbf{j}-3 t^{3} \mathbf{k 2 answers