题目
设f0(x)=sinx,f1(x)=f0′(x),f2(x)=f1′(x),…,fn+1(x)=fn′(x),n∈N,则f2 005(x)等于( )A.sinx B.-sinx C.cosx D.-cosx 答案:解析:f1(x)=(sinx)′=cosx,f2(x)=(cosx)′=-sinx, f3(x)=(-sinx)′=-cosx,f4(x)=(-cosx)′=sinx, 可知周期为4. ∴f2 005(x)=f1(x)=cosx.答案:C看拼音写词语
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