Chapter 3, Problem 212RE

Find the derivatives of $u\left(t\right),u\text{'}\left(t\right),u\text{'}\left(t\right)\times u\left(t\right)$ , $u\left(t\right)\times u\text{'}\left(t\right)$ and $u\left(t\right)\cdot u\text{'}\left(t\right)$ . Find the unit tangent vector.

212. $u\left(t\right)=\langle e^t,e^{-t}\rangle$