cos(-x)化简是-COS(X) SIN(-X)是SIN(X)

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cos(-x)化简是-COS(X)SIN(-X)是SIN(X)cos(-x)化简是-COS(X)SIN(-X)是SIN(X)cos(-x)化简是-COS(X)SIN(-X)是SIN(X)cos(-x)

cos(-x)化简是-COS(X) SIN(-X)是SIN(X)
cos(-x)化简是-COS(X) SIN(-X)是SIN(X)

cos(-x)化简是-COS(X) SIN(-X)是SIN(X)
cos(-x)化简是-COS(X)错!
应为:cos(-x)=cosx
SIN(-X)是SIN(X)错!
应为:sin(-x)=-sinx
这个可以结合“一全正二正弦三正切四余弦”的口诀,将“-x”看做第四象限角来判断