f(t)= f(t)coso(t-t)drdo 0兀 +0 f(t)sin ar d t sin at a() b()即 a() 0 1 f t( ) d f t ( )cos ( )    d   + − +   −     =   1 ( )cos d 1 ( )si s n d co sin t f t f           + − + − +   b()