O/p of opamp first is sine wave and o/p of opamp second is cosine ,as name implies quadrature is out of phase .in this way we can generate sine and cosine waves . For simplicity i have taken all R AND C equal and freq. Of oscillation i given by f=1/2pieRC at single frequency .the first opamp is acting non-inver. Integrator and second opamp is acting as inverting opamp.I have also connected one ac input ,practically noise is enough to create disturbance to create oscillations.
