1.求下列极限:-|||-(1) lim _(xarrow 0)dfrac (sin 2x)(x);-|||-(3) lim _(xarrow dfrac {pi )(2)}dfrac (cos x)(x-dfrac {pi )(2)}-|||-(2) lim _(xarrow 0)dfrac (sin {x)^3}({(sin x))^2};-|||-(4) lim _(xarrow 0)dfrac (tan x)(x);1.求下列极限:-|||-(1) lim _(xarrow 0)dfrac (sin 2x)(x);-|||-(3) lim _(xarrow dfrac {pi )(2)}dfrac (cos x)(x-dfrac {pi )(2)}-|||-(2) lim _(xarrow 0)dfrac (sin {x)^3}({(sin x))^2};-|||-(4) lim _(xarrow 0)dfrac (tan x)(x);