设((sin )^2x)=dfrac (x)(sin x)，求((sin )^2x)=dfrac (x)(sin x) .

(sin x)=dfrac (1)({cos )^2x} in (0,dfrac (pi )(2)),则(sin x)=dfrac (1)({cos )^2x}

求极限lim _(xarrow 0)(dfrac (1)({sin )^2x}-dfrac ({cos )^2x}({x)^2})= ()求极限

[题目]求 lim _(xarrow 0)(dfrac (1)({sin )^2x}-dfrac ({cos )^2x}({x)^2})

[题目]求 lim _(xarrow 0)(dfrac (1)({sin )^2x}-dfrac ({cos )^2x}({x)^2})

求极限；（3）lim _(xarrow 0)dfrac (sin 2x)(sin 5x)；求极限；（3）；

求lim _(xarrow 0)(dfrac (1)({sin )^2x}-dfrac (1)({x)^2}).求.

(3) lim _(xarrow 0)dfrac (sin 2x)(sin 5x);

5.求不定积分 int dfrac ({sin )^2x}(1+{sin )^2x}dx.

[题目] lim _(xarrow 0)(dfrac (1)({sin )^2x}-dfrac ({cos )^2x}({x)^2})= __

求lim _(xarrow dfrac {pi )(2)}dfrac (ln sin x)({(pi -2x))^2}求