用洛必达法则求下列极限:-|||-(9) lim _(xarrow +infty )dfrac (ln (1+dfrac {1)(x))}(arctan (x)-|||-(10) lim _(xarrow 0)dfrac (ln (1+{x)^2)}(sec x-cos x)-|||-(11)limxcot2x;-|||-(12) lim _(xarrow 0)(x)^2(e)^1/(x^2);