Braces on the left of latex braces in latex multiline formula

latex Left brace  latex Middle brace multiline formula
\begin{equation}
\left\{
             \begin{array}{lr}
             x=\dfrac{3\pi}{2}(1+2t)\cos(\dfrac{3\pi}{2}(1+2t)), &  \\
             y=s, & 0\leq s\leq L,|t|\leq1.\\
             z=\dfrac{3\pi}{2}(1+2t)\sin(\dfrac{3\pi}{2}(1+2t)), &  
             \end{array}
\right.
\end{equation}
 

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