f(0)是一个数值而不是函数.正确问法应该是f(x)五阶导数在0点的值.f(x)=x * sin2xf'(x)=sin2x+2xcos2xf''(x)=2cos2x+(2cos2x-4xsin2x)=4cos2x-4xsin2xf^(3)(x)=-8sin2x-4(sin2x+2xcos2x)=-12sin2x-8xcos2xf^(4)(x)=-2...