9.1 设 (x)=(int )_(0)^sin xsin 2tdt,g(x)=(int )_(0)^2tln (1+t)dt 则当x→0时,f(x )与g(x)相比-|||-是 ()-|||-(A)等价无穷小 (B)同阶但非等价无穷小-|||-(C)高阶无穷小 (D)低阶无穷小