Exercise 102

Are $\left[ \begin{smallmatrix} \cosh(t) \\ 1 \end{smallmatrix}\right]$, $\left[ \begin{smallmatrix} e^{t} \\ 1 \end{smallmatrix}\right]$, and $\left[ \begin{smallmatrix} e^{-t} \\ 1 \end{smallmatrix}\right]$ linearly independent? Justify.