As you do not have a single pair of delimiters here just put a blank line between the lines:

[tex]cos(x)[/tex]

[tex]sin(x)[/tex]

produces:

and:

[maTH]

\begin{array}{l}

\cos (x) \\ \\

\sin (x) \\

\end{array}

[/tex]

produces:

[maTH]

\begin{array}{l}

\cos (x) \\ \\

\sin (x) \\

\end{array}

[/tex]

RonL