Given $g ( x ) = \left\{ \begin{array} { c c } 3 & x < 1 \\\sqrt { x + 1 } & x \geq 1\end{array} \right.$

Given $g ( x ) = \left\{ \begin{array} { c c } 3 & x < 1 \\\sqrt { x + 1 } & x \geq 1\end{array} \right.$ Find $g \left( t ^ { 2 } - 1 \right)$