式中,a,a,b称为傅里叶系数,可由下列积分求得: 4=7/(0h=21((m) f(tcos katt f(t)cos katd(ot) f(t)sin kott = f(t)sin kotd(ot) 式(12-1)和式(12-2)各系数之间存在如下关系 Ao=ao (12 Pk = arctan k 4)式中, a0 , ak , bk称为傅里叶系数,可由下列积分求得:       = = = = = =              2 0 0 2 0 0 2 0 0 0 ( )sin ( ) 1 ( )sin 2 ( )cos ( ) 1 ( )cos 2 ( ) ( ) 2 1 ( ) 1 f t k tdt f t k t d t T b f t k tdt f t k t d t T a f t dt f t d t T a T k T k T (12 — 3) k k k km k k b a A a b A a arctan 2 2 0 0 = = + =  式（12 — 1）和式（12 — 2）各系数之间存在如下关系: (12 — 4)