This lecture delves into the analysis of static nonlinearity, focusing on the output behavior when the input is a sinusoidal signal. By approximating the input signal with its first harmonic, the equivalent gain is derived. The lecture explores the contradiction that arises and explains the correct approach to resolve it. Various values of amplitude and gain are compared, shedding light on the advantages of the proposed function over saturation. The lecture also covers the modeling of electronic circuits, behavior analysis using the first harmonic method, and determining oscillation parameters.