I plotted a graph on Origin software and need to do curve fitting to get accurate results. From my understanding, I need to provide a function for the fitting. So how do I derive the function? I am actually provided with the function I(x)=I0-I1cos(x-x0) and this function will fit the lowest part of my curve and the program will derive x0 which is the value of x when the y value is the lowest. On the other hand, the function I(x)=I2+I3cos(x-x1) will fit the highest part of the curve and x1 is the value of x when y is the highest. Can somebody explain those 2 functions and how the software fit the curve with it and how all this can be related to the Taylor's Series?