Forced undamped vibration

1. Nov 4, 2007

aritra

as we know ,the equation to the undamped forced vibration is
x=Asin{(w1+w2)/2}sin{(w1-w2)/2},the symbols have their usual meaning..but i can't understand how (w1+w2)/2 comes in picture in the phasor diagram...also its significance

2. Nov 4, 2007