f(a01)=4+∑ Bkm sin kat+∑ Ckm cos kat k=1 k=1 2丌 f(otd(ot) 2丌 2丌 B km f(ot)sin kotd(ot) 2丌 km f(ot)cos kotd(ot) 求出A、B、C可得原函数f(O)的展开式。   = = =    w w w  w w w  w w  2 0 2 0 2 0 0 ( ) cos ( ) 1 ( )sin ( ) 1 ( ) ( ) 2 1 C f t k t d t B f t k t d t A f t d t km km    =  =  = + + 1 1 0 ( ) sin cos k km k km f w t A B kw t C kw t 求出A0、Bkm、Ckm可得原函数 f (wt) 的展开式