二、计算 (int )_(0)^+infty (e)^-2x|sin x|dx

(int )_(e)^+infty dfrac (dx)(x{ln )^2x}= __

()-|||-(2) (int )_(-infty )^+infty dfrac (2x)(1+{x)^2}dx=lim _(aarrow +infty )(i

计算不定积分int (e)^x((3)^x+dfrac ({e)^-x}({sin )^2x})dx-|||-__.计算不定积分.

(int )_(0)^+infty dfrac (x{e)^-x}({(1+{e)^-x)}^2}dx= ()-|||-__

)int dfrac (1)({cos )^2x(sin )^2x}dx.

计算(int )_(0)^+infty dfrac (dx)({x)^2+4x+3}的值是A (int )_(0)^+infty dfrac (dx)({x)^

int dfrac (cos 2x)(cos x+sin x)dx

int dfrac (sin x)(1+{cos )^2x}dx=-|||-__

(int )_(0)^dfrac (pi {2)}sqrt (1-sin 2x)dx;

int dfrac (dx)(3+{sin )^2x}