If $$f\left( x \right) = \left| {\matrix{ {\cos x} & x & 1 \cr {2\sin x} & {{x^2}} & {2x} \cr {\tan x} & x & 1 \cr } } \right|,$ then $\mathop {\lim }\limits_{x \to 0} {{f'\left( x \right)} \over x}$$