def chirp(t, f0, t1, f1, method='linear', phi=0, vertex_zero=True):
 phase = _chirp_phase(t, f0, t1, f1, method, vertex_zero)
 phi *= (pi / 180)
 return cos((phase + phi))

def chirp ( t , f0 , t1 , f1 , method = 'linear' , phi = 0 , vertex_zero = True ) : phase = _chirp_phase ( t , f0 , t1 , f1 , method , vertex_zero ) phi *= ( pi / 180 ) return cos ( ( phase + phi ) )
frequency-swept cosine generator .