dx d 3. 均随时间周期性变化 dt dt 由x=Acos(t+q)得 X -AsIn(at +Po) dt d -A@coS(at +o) dt atx 3T/4 0 =1 88 3. 2 2 d d , d d , t x t x x 均随时间周期性变化 由 cos( ) =  +0 x A t 得 A ( t ) t x a 0 2 2 2 cos d d = = −   + A ( t ) t x v 0 sin d d = = −   + o t T a x T 2 v 3T 4 T 4 1 0 0 = =  