K1*S1*C1*(1+K3*S1+K4*C1+K5*C1*S1)/((1+K3*S1+K4*C1+K5*C1*S1)^2+K2*((1+K7*S1)/(1+K6*C1))^2*(1+K6*S1+K7*C1+K8*C1*S1)^2)