2.f'(=g(x),则dfsm2x)等于(） dx A.2g(x)sinx B.g(x)sin2x C.g(sin2x) D.g(sin2x)sin2x 解 么sn划=inin划 =f(sin2x)2sinxcosx =f(sin2x)sin2x =g(sinx)sin2x 故选D 4 2． f x g x ( ) ( ) = ,则 2 (sin ) d f x dx 等于( ) A. 2 ( )sin g x x B. g x x ( )sin 2 C. 2 g x (sin ) D. 2 g x x (sin )sin 2 解 2 2 2 (sin ) (sin )(sin ) d f x f x x dx =   2 = f x x x (sin )2sin cos 2 = f x x (sin )sin 2 2 = g x x (sin )sin 2 故选 D