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Given the function $f^{ \prime }\left( x \right) =\cos { \left( { x }^{ 2 }-1 \right) } ,$ find $f^{\prime\prime}(x)$.

$-\sin { ( { x }^{ 2 }-1 ) } $

$-2x\sin { ( { x }^{ 2 }-1 ) } $

$-2\sin { ( { x }^{ 2 }-1 ) } $

$2x\sin { ( { x }^{ 2 }-1 ) } $