A. $2x - 2\arctan x + C$
B. $x^2 - 2\arctan x + C$
C. $2x - 2\ln (1 + x^2)+ C$
D. $x^2 - 2\ln (1 + x^2)+ C$
(int )_(-1)^2x|x|dx=(int )_(-1)^1x|x|x+(int )_(1)^2x|x|x|=0+(int )_(1)^2(x)^2dx
求不定积分int dfrac (1)(2x)sqrt (ln x)dx=（）.int dfrac (1)(2x)sqrt (ln x)dx=int dfrac
(int )_(1)^2dfrac (dx)(x(1+sqrt {2x))}=( )A.(int )_(1)^2dfrac (dx)(x(1+sqrt {2x
()-|||-(2) (int )_(-infty )^+infty dfrac (2x)(1+{x)^2}dx=lim _(aarrow +infty )(i
int dfrac (1)(x{ln )^2x}dx
)int dfrac (1)({cos )^2x(sin )^2x}dx.
.int dfrac (1+{cos )^2x}(1+cos 2x)dx
( 单选题 ) int dfrac ({e)^x}(1+{e)^2x}dx=_________int dfrac ({e)^x}(1+{e)^2x}dx=int
(int )_(0)^dfrac (pi {4)}dfrac (x)(1+cos 2x)dx=( ) .(int )_(0)^dfrac (pi {4)}dfr
int dfrac (sin x)(1+{cos )^2x}dx=-|||-__