2元 Period of beat: T=- 02-01 Frequency of beat:==v-V. 2π x1=A cos@t=Acos2πYd x2=AC0s02t=A2cos2πt2 1 2 1 2 2 1 2 Period of beat: T Frequency of beat: x A t A t 1 1 1 1 2 1 cos cos x A t A t 2 2 2 2 2 2 cos cos