How to write a function by analysing/looking at a signal? Hello everyone. I have attached one waveform/signal. I want to know how can I represent it mathematically. I have been studying about functions that are already defined, say, a function like this f(x)=4Sinx + 2Cosx | x is in some degrees or radians. I shall draw a graph and I will know how it will look like. But I want to know the reverse. Like, say, I have a waveform(given/attached) and I want to represent it mathematically, so that I can apply my Calculus concepts and get the required solution that I want from this observed signal or just simply manipulate it according to my requirement. I have seen interpolation, which uses curve tracing or regression analysis. But by doing interpolation I think we are only trying to acquire a signal/waveform(we are approximating the signal). Let's say, I have approximated this signal and say, it looks like my waveform which I attached to this post. Now, the next step is that, I want to write the function i.e., I want to represent this function mathematically. How do I do that? Any concepts in mathematics that I can refer?