Let \[ f(x) = \begin{vmatrix} \cos x & x & 1 \\ 2 \sin x & x^3 & 2x \\ \tan x & x & 1 \end{vmatrix}, \] then \[ \lim_{x \to 0} \frac{f(x)}{x^2} = ? \]
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When faced with limits that result in indeterminate forms like 0/0 , use L’Hopital’s Rule to differentiate the numerator and denominator until a solvable limit is found.