偶延拓g(x)=∫(-x 则F(x) ∫f(x)0sx≤n f(-x)丌<X<0 f∫(x)的傅立叶余弦级数 f(x)4n+ a cos nr(0≤x≤x) 上一页下一页返回偶延拓 g(x) = f (−x)   =  + 1 0 cos 2 ( ) n an nx a f x (0  x   ) x y −  0  f (x) 的傅立叶余弦级数    − −     = ( ) 0 ( )0 ( ) f x x f x x F x   则